Thesis advisor: Fabio Ghironi / This dissertation consists of three essays on macroeconomics with frictions and uncertainty shocks. The first essay is "Collateral Constrained Workers' Unemployment". Financial market and labor market are closely interconnected each other in the sense that unemployed workers have difficulty not only in borrowing new loan but also in repaying outstanding loan. In addition, if unemployment entails loss from default and no new loan, credit constrained workers will accept lower wage to avoid the loss from losing job. In this paper, we try to investigate the role of the interaction between financial market and labor market over the business cycle. To do that, we assume credit constrained workers can borrow against their houses and repay outstanding loans only when they are employed. We also introduce labor search and matching framework into our model to consider unemployment and wage bargaining process explicitly. With this setup, we find that adverse housing preference shock leads to substantial negative impact on labor market by reducing the benefit from maintaining job. As a result, high unemployment significantly amplifies the business cycle by reducing supply of loan and increasing default. This result would be helpful to understand recent "Great Recession" which was originated from the collapse of housing market and accompanied by high unemployment and default rate. The second essay is "International Financial Business Cycles". Recent international macroeconomics literature on global imbalances explains the U.S. persistent current account deficit and emerging countries' surplus, i.e., the U.S. is the borrower. Little research has been done on the banking-sector level, where U.S. banks are lenders to banks in emerging countries. We build a two country framework where banks are explicitly modeled to investigate how lending in the banking sector can affect the international macroeconomy during the recent crisis. In steady state, banks in the developing country borrows from the U.S. banks. When the borrowers in the U.S. pay back less than contractually agreed and damage the balance sheet of the U.S. banks, with the presence of bank capital requirement constraint, U.S. banks raise lending rates and decrease the loans made to U.S. borrowers as well as banks in the developing country. The results are a sharp increase in the lending spread, a reduction in output and a depreciation in the real exchange rate of the developing country. They are the experience of many emerging Asian markets following the U.S. financial crisis starting in late 2007. Another feature of our model captures an empirical fact, documented by Devereux and Yetman (2010), that across different economies, countries with lower financial rating can suffer more when the lending country deleverages. The third essay is "Uncertainty, Collateral Constrained Borrowers, and Business Cycle". Standard RBC model fails to generate the co-movement of key macro variables under uncertainty shock because precautionary saving motive decreases consumption but increases investment and labor. To fill this gap, we build a DSGE model with collateral constrained borrowers who can borrow against housing and capital. In the model with modest risk aversion, we can generate the desired co-movement of key macro variables under uncertainty shock and the co-movement comes from the collateral constraint channel through drop in housing price. Under uncertainty shock, highly indebted borrowers sell collaterals to avoid uncertainty in future consumption. As a result, housing price goes down and it makes credit crunch to borrowers through collateral constraint channel. The negative effect of uncertainty shock is strengthened in the economy with higher indebted borrowers. / Thesis (PhD) — Boston College, 2012. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Economics.

Thesis advisor: Fabio Ghironi / Thesis advisor: Matteo Iacoviello / This dissertation studies the implications of housing market heterogeneity for the trans- mission of shocks, welfare and the conduct of monetary policy. In the first chapter I focus on mortgage contract heterogeneity (fixed vs. variable-rate mortgages). I develop and solve a New Keynesian dynamic stochastic general equilibrium model that features a housing market and a group of constrained individuals who need housing collateral to obtain loans. A given proportion of constrained households borrows at a variable rate, while the rest borrows at a fixed rate. The model predicts that in an economy with mostly variable-rate mortgages, an exogenous interest rate shock has larger effects on borrowers than in a fixed-rate economy. For plausible parametrizations, aggregate differences are muted by wealth effects on labor supply and by the presence of savers. More persistent shocks cause larger aggregate differences. From a normative perspective I find that, in the presence of collateral constraints, the optimal Taylor rule is less aggressive against inflation than in the standard sticky-price model. Furthermore, for given monetary policy, a high proportion of fixed-rate mortgages is welfare enhancing. Then, I develop a two-country version of the model to study the implications of housing market heterogeneity for a monetary union as well as costs and benefits of being in a monetary union when there are asymmetric shocks. Results show that consumption reacts more strongly to common shocks in countries with high loan-to-value ratios (LTVs), a high proportion of borrowers or variable-rate mortgages. I also find that country-specific housing price shocks increase consumption not only in the country where the shock takes place. Welfare analysis shows that housing-market homogeneization is not beneficial per se, only when it is towards low LTVs or predominantly fixed-rate mortgages. As for costs and benefits of monetary unions, when there is a technology shock in one of the countries and they are symmetric, the monetary union regime is welfare worsening. However, results are dependent on whether or not countries are symmetric and on the source of the asymmetry. / Thesis (PhD) — Boston College, 2008. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Economics.

This thesis aims to understand the role of interest rate setting behavior of the banks for the transmission of technology, monetary policy and loan rate shocks into the real economy. To this end, we introduce a monopolistically competitive banking sector into a New Keynesian model. Here, each bank can change its loan rate only infrequently in the fashion of Calvo type staggered contract. This setting implies that the adjustment of the aggregate loan rate is sticky, which is consistent with the empirical evidence. The results show that having sticky adjustment in the loan market changes the dynamics of the model significantly. Following each shock, the sluggish adjustment of the loan rate affects the amount of loan used by the borrowers considerably. This is the main reason behind the differentials across the impulse responses of the model with sticky loan rate and flexible loan rate.

La contrazione della formazione di imprese dopo la crisi finanziaria del 2008 è stata in parte determinata dall'inasprimento degli standard creditizi. Incorporare l'imperfezione del mercato del credito nei modelli DSGE è diventato un passo essenziale verso una migliore spiegazione di tali risultati. Nel primo capitolo, indago sul ruolo del finanziamento esterno nella creazione d'impresa. Sottolineo l'impatto del potere di mercato delle banche e la presenza di dispersione tra i tassi di interesse dei grandi e dei piccoli prestiti all'ingresso. Pertanto, sviluppo un modello DSGE che collega l'ingresso dell'impresa al sistema bancario imperfetto e introduco costi di prestito eterogenei per operatori storici e nuovi. Il modello prevede un impatto amplificato degli shock reali e finanziari e mostra una maggiore volatilità man mano che lo spread dei tassi di interesse si allarga. In linea con l'evidenza, la versione sticky-price produce un'entrata prociclica in risposta allo shock monetario espansivo. Nel secondo capitolo, mi concentro sull'interazione tra i prezzi delle case, le insolvenze sui prestiti e l'ingresso di imprese. Presento prove SVAR che rivelano una risposta prociclica positiva della nascita allo shock dei prezzi delle case e una reazione negativa alle inadempienze sui prestiti. Quindi sviluppo un modello DSGE in grado di prevedere e spiegare queste risposte. L'endogeneità del vincolo collaterale e della creazione d'impresa è al centro del meccanismo del modello. Il modello genera dei secondi momenti ragionevolmente vicini alle controparti dei dati. / The contraction of business formation after 2008 financial crisis was driven partly by the tightened credit standards. Incorporating credit market imperfection to DSGE models became an essential step towards better explaining such outcomes. In the first chapter, I investigate the role of external financing in firm creation. I highlight the impact of bank market power, and the presence of dispersion between interest rates of large and small loans on entry. Therefore, I develop a DSGE model linking firm entry to imperfect banking system, and introduce heterogeneous borrowing costs for incumbents and entrants. The model predicts amplified impact of real and financial shocks, and exhibits higher volatility as the spread in interest rates gets wider. In line with evidence, the sticky-price version produces pro-cyclical entry in response to expansionary monetary shock. In the second chapter, I focus on the interaction between house prices, loan defaults, and firm entry. I present SVAR evidence that reveals positive pro-cyclical response of birth to house price shock, and negative reaction to loan defaults. Then I develop a DSGE model that is able to predict and explain these responses. The endogeneity of collateral constraint and firm creation is in the core of the model’s mechanism. The model generates some second moments that are reasonably close to their data counterparts.

Questa tesi esamina l’interazione tra aspettative eterogenee e il rapporto creditore-debitore. In letteratura, non è ancora chiara la natura dell’interazione tra cicli del credito e aspettative individuali. Per questo motivo ho capito che sarebbe stato importante iniziare dai lavori seminali in entrambi i campi, ovvero Kiyotaki & Moore (1997) e Brock & Hommes (1997). Il mio principale obbiettivo è stato quello di studiare più nel dettaglio il funzionamento del vincolo di garanzia. Il fil rouge dell’intera tesi, infatti, è l’analisi del ruolo delle frizioni finanziarie nell’andamento del prezzo di un asset collateralizzato. In particolare, presento un modello dove l’ipotesi di aspettative razionali viene abbandonata. I risultati del primo capitolo rivelano che le aspettative individuali sono una fonte importante di instabilità, anche se la configurazione iniziale risulta stabile. L’elemento che provoca questa instabilità è la bancarotta causata dalla divergenza tra le aspettative di creditori e debitori sul prezzo dell’asset collateralizzato. Poi, nel secondo capitolo, effettuo un esperimento di learning-to-forecast. Fondato sul modello del primo capitolo, ha come obbiettivo quello di testare se e come la volatilità è legata alle percezioni di rischio dei creditori. Ciò che emerge è che ridurre il credito in risposta ad un aumento delle insolvenze in realtà conduce a scenari addirittura peggiori dove il benessere totale si deteriora e il numero delle bancarotte aumenta. / This thesis examines the interaction between heterogeneous expectations and the borrower-lender relationship. In the literature, the nature of the interaction between credit cycle and individual expectations is still unclear. Therefore I realized it was important to start from the seminal works in both fields, that is Kiyotaki & Moore (1997) and Brock & Hommes (1997). My main concern has been to gain insights into the collateral constraint. The common thread of the whole thesis, indeed, is to analyse the role of financial frictions in the price development of a collateralized asset. In particular, I introduce a model where rational expectations are dropped. The results of the first chapter reveal that even in a simple and stable setting, individual beliefs are an important source of instability. The driver of this instability is the bankruptcy caused by the divergence between borrowers' and lenders' price expectations on a collateralized asset. Then, I conduct an online learning-to-forecast experiment. Founded on the model of the first chapter, it tests whether and how volatility is related to lender-level risk perceptions. What emerges is that to shrink credit in response to an increase in defaults actually leads to worse scenarios where total welfare deteriorates and the number of bankruptcies increases.