Con questa ricerca si sono volute ripercorrere le diverse fasi storiche e le motivazioni che, nel corso del Novecento, hanno portato la razza bovina Frisona Italiana, conosciuta per la sua alta produttività lattifera, ad affermarsi come la più allevata sul territorio della Penisola. Al di là di una ricostruzione fattuale si sono volute comprendere le strategie dell’innovazione tecnologica in campo zootecnico negli ultimi decenni. Il lavoro prende avvio dall’emergere tra Sei e Ottocento in Gran Bretagna, nei Paesi Bassi e negli Stati Uniti di una speciale attenzione alla riproduzione animale. Viene poi analizzata l’introduzione in Italia di capi Friesian olandesi a partire dalla fine dell’800 e di quelli Holstein-Friesian nordamericani nel periodo tra le due Guerre Mondiali. Infine viene ricostruita l’opera di miglioramento della popolazione in esame, arrivando a una nuova sottorazza, col tempo divenuta oggetto anche di esportazione. Nel lavoro viene analizzato infine il ruolo delle istituzioni e dell’associazionismo, amplificatosi dopo la seconda guerra mondiale, tramite la ricostruzione dei rapporti dialettici tra queste istituzioni collettive da un lato e gli ispettorati agrari e il MAF dall’altro, in ordine alla gestione dei libri genealogici e alla definizione degli indirizzi zootecnici. / With this research we wanted to reconstruct the different historical phases and the reasons that, during the XX century, led the Italian Friesian breed of cow, known for its high milk productivity, to become the most widespread breed on the Peninsula. Besides a reconstruction of the facts, we wanted to understand the strategies for the technological innovation in the field of zootechnics during the last ten years. The work starts with the emergence, between the XVII and the XIX century in Great Britain, in the Low Countries and in the United States of a special attention for animal reproduction. Then, we examined the introduction in Italy of Dutch Friesian heads, from the end of the XIX century, and of North-American Holstein-Friesian, in the period between the two world wars. Finally, we reconstructed the process of improvement of the population here analysed, which led to a new sub-breed, later exported. Finally, we analysed the role of institutions and associations, increased after the Second World War, by reconstructing the relations between them.

Although the last thirty years Regional Innovation Systems (RIS) received great attention by policy makers, only during the last decade social networks were applied in the fields of innovation and regional economics. The majority of the existing empirical studies on networks adopt a static point of view, representing a regional knowledge network at a certain point in time, while there are few recent attempts exploring the evolution of knowledge networks and the dynamics that drive it. The present work aims at covering some of the gaps in the literature, using the dataset on collaborative projects from the ICT activity in Trentino. It introduces an original multidimensional framework to analyze the knowledge flows inside, from within and towards the regional network. It also identifies the key actors inside the region and describes their role in knowledge creation and diffusion. Concerning the spatial and temporal evolution of the knowledge networks, this thesis investigates the preferences of the economic actors operating inside regional networks, in terms of shared characteristics, while it explores the dynamics developed through time by the behavior of economic agents during high and low certainty periods, contributing to the inertia and the resilience of the regional knowledge network. The present research is the first that introduces Social Network Analysis (SNA) using data on knowledge transfer from Trentino, considering the entire universe of actors involved in the regional ICT knowledge network for the last fifteen years, and allocating it to an original multidimensional framework, in order to reveal the value of the knowledge network per se, and the impact of the regional policies on the network and not on the output of the innovation process. On the spatial evolution of networks, it explores in depth the preferences of the actors of a regional knowledge network, in order to make it more solid through strong collaborations. It proves that the effect of every kind of proximity or distance is different, while it introduces the measure of relational proximity, exploring the effect of the position of an actor inside the knowledge network in relation with the rest of the actors. However, the major finding of this thesis is the introduction of the temporal aspect in the evolution of the regional knowledge network, and the exploration of the agent behavior during periods of uncertainty. The introduction in the network evolution of an external negative event, like economic crisis, allows the deduction of useful conclusions on how the actors behave in terms of trust and collaboration creation.

This thesis contains four closely related essays which address the empirical issues pertaining to the causes, consequences, and households’ responses to food price shocks in Uganda. The first essay investigates the nature of volatilities in agricultural commodity prices in Uganda between 2000 and 2012 by focusing on six key food staples, namely matooke, cassava, maize, sweet potatoes, beans, and millet flour. It studies the behavior of monthly price volatilities of these commodities, examines the extent of their volatility spillovers, identifies their macroeconomic and environmental drivers, and uncover their differential impacts using respectively the General Autoregressive Conditional Heteroscedastic (GARCH), the Vector Autoregressive (VAR) and the Seemingly Unrelated Regression (SUR) models. I find evidence that both unconditional and conditional price volatilities have significantly increased since January 2008 for most commodities, period of turmoil in the global food markets. The GARCH (1, 1) estimates indicate a strong persistence in volatility for most commodities while results from the Exponential GARCH (1, 1) models suggest the presence of asymmetric and leverage effects of unexpected price shocks for half of the commodities. In addition, the VAR estimation results detect limited and mostly unidirectional spillover effects across food commodities. Finally, historical price volatilities of most commodities are found to be primarily affected by volatilities in consumer price indices, fuel prices, and rainfall, with less evidence of strong seasonality effects as previously reported. The second essay presents an empirical analysis of the welfare impacts of food price changes in Uganda using three waves of the Uganda National Panel Surveys (UNPS) spanning over the years 2005-2011. It theoretically investigates the implications of labor market imperfections and households’ heterogeneity in terms of their net positions in both food and labor markets and compares welfare estimates between separable and non-separable models. Through the estimations a panel stochastic production frontier function and a censored-Quadratic Almost Ideal Demand Systems (QUAIDS) with expenditure and shadow wage endogeneities, the results suggest that the welfare effects of price changes (measured in terms of compensating variations) were globally lower in the non-separable agricultural model, implying a high degree of labor market frictions. Furthermore, I find that the welfare effects were unevenly distributed both within and between household groups. Particularly, although agricultural households benefited from price increases as a group between 2005/6 and 2009/10, both significant and insignificant net buyers did suffer from price changes. Moreover, results from non-parametric estimations show that households at the extremes of the welfare distribution were more severely hit by food price instabilities than others. Finally, the essay suggests that the important dynamics in the net market positions observed during the sample period might be attributed to a cost-benefit analysis related to the potential welfare effects of food prices. The third essay explores the question of crop choices and land allocations in environments where farmers face uncertainties about end-of-season output prices and yield levels, weather variability, and formulate expectations about their future levels. Indeed, in the absence of credit and/or insurance markets, farmers are widely expected to adjust their land allocation decisions as a management tool against agricultural and market-related risks. However, little is actually known about the likely differential effects of each of these risk components on farmers’ decisions, particularly when current decisions are allowed to depend on previous choices. Using a nationally representative panel data set for agricultural households in Uganda spanning over the years 2005 – 2012, the paper proposes to investigate the role played by both price and yield risks on farmers’ crop choices and area allocations using a multivariate generalization of the Heckman-type two-step procedure: a multivariate crop selection and a conditional acreage share models. The crop selection problem is modeled as a dynamic multivariate probit regression and estimated through Simulated Maximum Likelihood and the Geweke Hajivassiliou Keane simulator, whereas the conditional acreage share model is estimated using a dynamic multivariate fractional logit model. In both the multivariate crop selection and acreage share models, the results reveal that, while own expected prices and yields are among the main drivers of farmers' crop choices and land share allocations, farmers are found to be more sensitive to changes in expected yield levels than in expected end-of-season output prices. In addition, yield risks, temperature and rainfall volatility appear to have more impact on acreage share decisions than market price risks. Finally, household characteristics are found to play a marginal role in explaining farmers’ crop selection and acreage allocation decisions. The fourth and last essay develops a modified standard Ramsey model to analyze households’ welfare growth and test the assumption that differential exposure to food price shocks leads to different welfare trajectories and to potentially increased risks of poverty traps. The essay focuses on two welfare indicators, namely consumption levels and asset indices, and employs a battery of econometric methods, ranging from parametric GMM fixed effects models to locally weighted scatterplot smoother (LOWESS), local polynomial regressions, and Ruppert et al’s (2003) semi-parametric penalized splines to address nonlinearities in welfare dynamics, identify and locate critical welfare thresholds, and test for the presence of single against multiple welfare equilibria. Using the full sample, I find nonlinearities in welfare dynamic paths and reduction in the growth rates of both consumption levels and assets holdings as a consequence of exposure to food price and asset shocks. However, there is no evidence of poverty traps caused by households’ exposure or vulnerability to food price shocks, but instead I identify only a single dynamic stable equilibrium, located slightly above the official poverty, towards which Ugandan households are converging in the long run. Finally, when disaggregating households into different sub-groups sharing similar characteristics, the empirical results reveal that Ugandan households are converging towards specific welfare equilibria, depending on their initial conditions, demographic characteristics, the extent of their vulnerability and differential exposure to food price shocks. Particularly, I found that, households exposed to food price shocks or above the vulnerability threshold index are expected to move in the long run to welfare equilibria located at lower levels than their unexposed or less vulnerable counterparts.

The analysis of the complex and fast changing technological processes which today are summarized in the term ‘Industry 4.0’ reveals that the industrial system is shifting towards a new technological paradigm (Perez, 2009; 2010), implying systemic transformations at micro, meso and macro levels of analysis (Geels, 2005). These radical transformations are deeply changing the way products, production processes and business models are conceived, questioning the traditional separation between manufacturing and services, and making it more and more important for firms to adopt a collaborative approach to innovation (Hagedoorn et al., 2000). This rapid technological advance implies the need for the socio-economic players to adopt new strategic and operational measures in order to prevent the loss of competitive advantage of national and regional innovation systems. The recent debate on industrial policies shows that a mission-oriented industrial policy approach (Mazzucato, 2014; European Commission, 2018) may provide interesting inspirational principles able to guide these transformations, since it places at the centre of its reasoning the key role of the public actor able to stimulate the strategic coordination between multiple socio-economic players at different levels (Mazzucato and Perez, 2014; Rodrik, 2004). According to this approach, Public-Private research Partnerships, are assumed to be effective vehicles of governance able to improve technological development, stimulating strong links between the relevant socio-economic players and thus increasing the national and regional systems’ overall innovative potential (Mazzucato, 2014; Rodrik, 2004; 2014; Robin and Schubert, 2013; Kristensen and Scherrer, 2016). The aim of the present work is to understand how the strategic coordination between public and private players may be an opportunity for the definition of effective innovation policies in the context of the current socio-technical transition. In order to reach this purpose, a multilevel approach (Geels, 2005) is adopted, taking into account both the national and the regional levels of analysis. A quantitative analysis is provided at national level in order to understand the relationship between a specific approach to innovation and technology policy, the overall innovation performance and the level of diffusion of cooperative innovation activities in a National Innovation System (Lundvall, 1988); moreover, it contributes to the existing literature on Public-Private research Partnerships (Hagedoorn et al., 2000) by testing the effectiveness of some main variables at industry and company level explaining the propensity of companies to get involved in formal cooperative innovation activities. This analysis is made taking into account data stemming from the 8th wave of the Community Innovation Survey, 2010-2012. Moreover, the results of a field research conducted at regional level are presented, aiming at understanding the elements of an institutional/organizational framework which are able to positively influence technological local development. In this case, the analysis takes into account a Regional Innovation System (Cooke et al., 1997): the Autonomous Province of Trento. Data have been gathered through both primary sources, based on 57 semi-structured interviews to local institutions and firms, and secondary sources, based on relevant documents and reports. The major conclusion of the present work is that, given the systemic nature of this socio-technical transition, only a mission-oriented policy approach to innovation policy based on strategic Public-Private research Partnerships may be able to trigger the necessary cross-level synergies between the different socio-economic players involved, managing the important challenges lying behind these transformations.

Financial constraints and limited access to markets are the most important obstacles for economic development in developing economies that are largely dependent on agriculture. Lack of access to credit and output markets, in particular, is frequently identified as a key barrier to transformation of subsistence agriculture. The fundamental problems are related to information asymmetry, lack of collateral and limited economies of scale. Innovative institutional mechanisms, in the form of microfinance and producer organizations, offer ways to address information asymmetry and increase scale economies. This dissertation examines the outreach, financial performance and impact of microfinance institutions as well as the key drivers of agricultural cooperatives and its impact on smallholder farmers efficiency in Ethiopia. To meet these objectives four data sets from Ethiopia, one institutional and three household survey data, are used. The analysis of microfinance generally focuses on examining the trade-offs between outreach to the poor and financial sustainability by ownership forms (shareholder owned vs. memberowned). The outreach-financial sustainability trade-offs analyzed first using the institutional survey data. The empirical results show that serving the poor and financial sustainability are challenging objectives to achieve together. There is also evidence that suggests the presence of mission drift. Second, the role of ownership form on outreach, financial performance and cost-efficiency is analyzed within the framework of efficient ownership assignment theories using regression and stochastic cost frontier approaches. This analysis aims at testing whether the commonly held proposition of greater efficiency of shareholder firms in microfinance by policy advocates is empirically supported. The results reject the superiority of shareholder-owned microfinance over financial cooperatives. In fact, the evidence here supports the advantages of member-owned microfinance on cost efficiency and balancing the double bottom-lines of microfinance. Third, the impact of access to microfinance credit on farmers investment on agricultural inputs is assessed using propensity score matching (PSM) and control-function-regression methods that address potential participation selection biases. Results from both approaches show that access to credit increased the use of productivity enhancing inputs among borrower farmers. Indeed, farmers that borrow from financial cooperatives tend to invest more on modern inputs. The analysis of agricultural cooperatives tested theoretical propositions from organizational and the new institutional economics theories on the drivers of agricultural cooperatives incidence and farmers membership and patronage decisions. Discrete choice models are employed for the empirical analysis. The results indicate that the incidence of agricultural cooperatives in Ethiopia is more related to the countervailing market power argument than to the transaction cost reduction hypothesis. Despite open membership polices, the analysis on farmers participation indicates that membership and patronage decisions are related and significantly influenced by location, asset and relational specificities. Finally, the impact analysis estimated technical efficiency gains of membership in agricultural cooperatives and employed matching and stochastic production frontier techniques. The evidence suggests that membership in agricultural cooperatives significantly enhances efficiency gains among smallholder farmers.

L'energia rappresenta un elemento fondamentale dell'architettura economica della regione euro-mediterranea. Tuttavia, le relazioni energetiche regionali non sono mai state analizzate all'interno di un comprensivo quadro analitico capace valutare il potenziale ruolo dell'energia come catalizzatore di nuove forme di cooperazione economica e politica a livello regionale. Questa tesi aspira a colmare questa lacuna della letteratura esistente, fornendo un'analisi basata sulla seguente domanda di ricerca: può un nuovo schema di relazioni energetiche euro-mediterranee rafforzare l'integrazione economica e politica della regione? Questa domanda di ricerca viene esplorata applicando gli strumenti analitici forniti da International Political Economy e funzionalismo a due casi studio rappresentanti i più importanti progetti di cooperazione energetica mai tentati nella regione: Nabucco e Desertec. Questa analisi non solo consente di trovare una risposta precisa alla suddetta domanda di ricerca, ma permette altresì di definire una serie di policy recommendations disegnate per aprire la strada ad un nuovo schema di cooperazione energetica euro-mediterranea finalizzato a rafforzare la più ampia integrazione economica e politica della regione. / Energy represents a cornerstone in the Euro-Mediterranean economic architecture. However, the regional energy relations have never been framed into a comprehensive analytical framework able to assess the actual potential role of energy in acting as a catalyst for the overall regional economic and political cooperation. This thesis aspires to fill this research gap by providing an analysis based on the following research question: could a new Euro-Mediterranean energy relations scheme strengthen the economic and political integration of the overall region? This research question is explored by applying the analytical tools provided by International Political Economy and Functionalism to two empirical case studies representing the most important energy cooperation projects ever attempted in the region: Nabucco and Desertec. This analysis not only allows to find an accurate answer to the research question, but it also permits to define a set of policy recommendations aimed at paving the way for a new Euro-Mediterranean energy cooperation scheme designed to strengthen the economic integration of the overall region.

Waldo Tobler, con la sua prima legge della geografia, afferma “Ogni cosa è correlata con qualsiasi altra, ma le cose vicine sono più relazionate di quelle lontane" (Tobler, 1970). Se questo era certamente vero nel 1970, tale convinzione è stata messa in discussione con l’avvento delle Tecnologie dell’Informazione e della Comunicazione (ICT). Nel dibattito riguardo al processo di globalizzazione molti studiosi e giornalisti sostengono infatti che, con la velocizzazione delle telecomunicazioni, la distanza fisica è destinata a perdere il proprio potere esplicativo relativamente a molti fenomeni socio-economici (Cairncross, 2001; Friedman, 2005). Questa dissertazione vuole contribuire al dibattito rispondendo, seppure parzialmente, alla domanda “La distanza importa ancora?” e definire alcune possibili implicazioni di policy. L’obiettivo è quello di mostrare il ruolo della distanza geografica in tre diversi contesti economici caratterizzati da differenti dimensioni dell’unità di analisi. I risultati suggeriscono che, anche se su scala globale lo sviluppo delle nuove tecnologie ha modificato la percezione individuale della distanza come deterrente alle interazioni, lo spazio geografico mantiene ancora la sua rilevanza del definire le relazioni socio-economiche locali, aumentando il ruolo di città e regioni quali centri della maggioranza delle attività economiche. / Waldo Tobler, with his first law of geography, stated “Everything is related to everything else, but near things are more related than distant things" (Tobler, 1970). If it was certainly true in 1970, this belief is called into question in an era of development of Information and Communication Technologies (ICTs). In the debate over globalization processes, several scholars and journalists argue indeed that, with the increasing speed of telecommunications, physical distance is losing its explanatory power as determinant of socio-economical relationships (Cairncross, 2001; Friedman, 2005). This dissertation aims to give a contribution to this debate, partially answering to the broad question “Does distance still matter?" and to draw possible policy implications. The purpose is to show the role of geographical distance in three different economic environments, characterized by diversified size of the unit of analysis. Results suggest that, even if at a global scale improvements in ICTs have changed the individual perception of the distance as deterrent in interactions, geographical space still maintains its relevance in defining local socio-economic relationships, increasing the role of cities and regions as the core of most of economic activities.

La tesi propone evidenze empiriche e teoriche sull’importanza delle abilità cosiddette non cognitive come elemento fondamentale del capitale umano individuale. In particolare, ci si propone di discutere se, e in che portata, queste capacità relazionali incidano sulle performance lavorative e sulle decisioni concernenti la salute. La tesi propone le reti sociali, o “social networks”, come possibile misurazione di queste capacità interpersonali. Il primo capitolo presenta una dettagliata rassegna della letteratura sulle abilità non cognitive, e sui loro effetti su salari e stato di salute, e discute l’appropriatezza dell’utilizzo delle variabili di “social networks” come misura per tali abilità. Il secondo capitolo stima a livello empirico l’impatto delle capacità relazionali sui salari. Per una completezza di metodologia e per verificare la robustezza dei risultati, le stime vengono effettuate con diverse metodologie econometriche. Il terzo capitolo analizza gli effetti di queste abilità sociali sul consumo di sigarette, e discute la loro importanza rispetto ad altri fattori rilevanti, come tasse e comportamenti dei genitori. Il capitolo applica diversi stimatori, lineari e non, ed esamina le differenze, in termini di grandezza e significatività statistica, nei risultati ottenuti. / This thesis provides further evidence on the importance of including non-cognitive and social skills as a component of individual human capital. In particular, it aims to assess whether interpersonal skills, measured through social network metrics, influence labour market and health attainment. The first chapter reviews the literature on non-cognitive skills and their impact on various outcomes, and discusses the use of social network metrics as measure of interpersonal skills. The second chapter empirically estimates the impact of these social skills on earnings. The effect is estimated comparing alternative empirical strategies to model social interactions, to fully examine the robustness and the meaning of the results obtained. The third chapter examines the effect of these skills on individual smoking behaviour over the young adulthood life. In particular, it examines the role of popularity and social skills on smoking decision, and compares the relative importance of these skills to other factors, such as cigarette taxes, and parents’ smoking behaviour. It also analysed the extent to which using non-linear estimators affects the significance and the magnitude of the effects of these factors.

All’interno del quadro teorico del Capability Approach ‘agency’ viene definito come ciò che permette agli individui di raggiungere i propri obiettivi. Quando il concetto di ‘agency’ viene studiato attraverso misure soggettive, insorge il problema delle preferenze adattive. Lo scopo di questa Tesi è di testare una metodologia che possa catturare la percezione individuale di ‘agency’ nelle diverse dimensioni che compongono la nostra vita, limitando i problemi di misurazione dovuti delle preferenze adattive. Per questo fine, ci affidiamo al ‘Relative Autonomy Index’. Inoltre, utilizziamo la metodologia di ‘Achoring Vignette’ per aumentare la comparabilità tra le percezioni dei singoli individui. Nella prima parte, indaghiamo se il nostro metodo effettivamente riduce l’incomparabilità individuale attraverso uno studio pilota. I risultati dimostrano come il nostro metodo sia in grado di catturare differenze nel comportamento di risposta. Nella seconda parte, sulla base di una seconda raccolta di dati, applichiamo la nostra metodologia al fine di indagare l'impatto dei Gruppi di Acquisto Solidale sul livello di autonomia di un gruppo di produttori italiani. I nostri risultati indicano che il coinvolgimento con i Gruppi di Acquisto Solidale evita la riduzione dell'autonomia percepita dai quei produttori che non sono coinvolti con i Gruppi di Acquisto Solidale. / Within the Capability Approach, agency is one of the components that enable individuals to be empowered. When subjective measures are applied to the study of agency, the problem of ‘adaptive preferences’ arises. The aim of this thesis is to test a methodology that captures the individual perception of agency, while taking into account the bias coming from adaptive preferences. We rely on the Relative Autonomy Index to capture the individual’s agency in several dimensions. In addition, in order to increase the comparability between the individual’s perceptions, we employ the Anchoring Vignette methodology. We investigate whether our methodology reduces the individual incomparability through a pilot study. The results of this preliminary exercises show that our methodology is able to capture dissimilarities in response behaviours. Through a second data collection, we apply our methodology in order to investigate the impact that the commercial relationship between Solidarity Purchasing Group and Italian producers has on the latter. Our findings suggest that the involvement in the Solidarity Purchasing Group has a mainly positive impact on producers’ level of autonomy, which remains at lower levels for producers that did not develop a relationship with the Solidarity Purchasing Group.

A partire dagli anni ’80, la diffusione dei metodi statistici, abbinata ai progressi nelle capacità computazionali dei personal computers, ha progressivamente facilitato i ricercatori nel testare empiricamente le proprie teorie. Gli economisti sono diventati in grado di eseguire milioni di regressioni prima di pranzo senza abbandonare le proprie scrivanie. Purtroppo, ciò ha portato ad un accumulo di evidenze spesso eterogenee, quando non contradditorie se non esplicitamente in conflitto. Per affrontare il problema, questa tesi fornirà una panoramica dei metodi meta-analitici disponibili in economia. Nella prima parte verranno introdotte le intuizioni alla base dei modelli gerarchici a fattori fissi e casuali capaci di risolvere le problematicità derivanti dalla presenza di osservazioni non indipendenti. Verrà inoltre affrontato il tema dell’errore sistematico di pubblicazione in presenza di elevata eterogeneità tra gli studi. La metodologia verrà successivamente applicata, nella seconda e terza parte, a due diverse aree della letteratura economica: l’impatto del rapporto banca-impresa sulle prestazioni aziendali e il dibattito sulla relazione fra democrazia e crescita. Mentre nel primo caso la correlazione negativa non è influenzata da fattori specifici ai singoli paesi, il contrario è vero per spiegare l’impatto (statisticamente non significativo) delle istituzioni democratiche sullo sviluppo economico. Quali siano questi fattori è però meno chiaro; gli studiosi non hanno ancora individuato le co-variate – o la corretta misurazione di esse – capaci di spiegare questa discussa relazione. / Starting in the late 1980s, improved computing performances and spread knowledge of statistical methods allowed researchers to put their theories to test. Formerly constrained economists became able [to] run millions of regressions before lunch without leaving their desks. Unfortunately, this led to an accumulation of often conflicting evidences. To address such issue, this thesis will provide an overview of the meta-analysis methods available in economics. The first paper will explain the intuitions behind fixed and random effects models in such a framework. It will then detail how multilevel modelling can help overcome hierarchical dependence issues. Finally, it will address the problem of publication bias in presence of high between-studies heterogeneity. Such methods will be then applied, in the second and third papers, to two different areas of the economics literature: the effect of relationship banking on firm performances and the democracy and growth conundrum. Results are far-reaching. While in the first case the documented negative relation is not driven by country-specific characteristics the opposite is true for the (statistically insignificant) impact of democratic institutions on economic growth. What these characteristics are is, however, less clear. Scholars have not yet found the covariates - or their suitable proxies - that matter to explain such much-debated relationship.