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In these papers I discuss the causal estimation of the effects of fertility and fertility planning developments on mother and child outcomes. A number of concerns are raised with existing identification techniques, and alternative methodologies to consistently estimate the effect of interest are proposed. These concerns and new techniques are illustrated using microdata on slightly more than 43,000,000 births ocurring between 1972 and 2013. In the first substantive chapter (written with Sonia Bhalotra), we discuss the validity of the use of twin births in fertility research. We demonstrate that twin births are not random. Successfully taking twins to term depends upon positive maternal health behaviours and investments in the periods preceding birth. We show that this is of considerable concern for estimation techniques which rely on twin births being (conditionally) randomly assigned to identify causal effects. To illustrate, we consider the estimation of the child quantity-quality (QQ) trade-off, and show that existing instrumental variable estimates are inconsistent in the contexts examined. Upon partially correcting for the fact that twin births are not random, a statistically significant QQ trade-off begins to emerge. We close by examining a number of partial identification techniques to bound the true effect of fertility on child outcomes. In the second substantive chapter, I examine the effect of fertility control policies on the fertility decisions and outcomes of women. I consider the case of the emergency contraceptive pill in Chile. The staggered arrival of this technology to Chile over the last decade has resulted in the availability of the first safe and legal post-coital birth control policies. In a context of high teenage pregnancy rates, difference-in-difference (DD) style estimates suggest that this policy has accounted for reductions in short-term teen childbearing by as much as 7%, an effect similar to the arrival of abortion in the USA. This policy is also shown to reduce fetal deaths reported in early gestation with no similar reduction in late gestation: suggestive evidence that an alternative fertility control policy may reduce costly and dangerous illegal abortions. Finally, I turn to the use of DD estimators as a policy-analysis tool. I discuss how such estimators perform in the case of reforms which may not be sharply demarcated to treatment and control clusters, but rather subject to local spillovers or externalities. I propose an extension of the typical DD estimator: a spillover-robust DD estimator. This methodology is applied to estimate the effect of two localised fertility control reforms in Mexico and Chile, where women close to treatment clusters who were not themselves subject to the reform may nonetheless travel to access treatment.

This thesis aimed at measuring the economic costs of soil degradation and to determine factors that influence the incidence and extent of adoption of soil conservation technologies by smallholder farmers in Malawi. A dynamic optimisation model was used to derive and analyse the optimal conditions for soil resource extraction and use in Malawi, while a selective tobit model was used to simulate the two-step decision-making process of farmers with respect to adoption of soil conservation technologies. Soil degradation has long-term consequences and static models, which form the bulk of studies that have so far been carried out in Africa on this topic, do not account for the inter-temporal dimension of optimal resource management. To deal with this shortcoming, this thesis used an inter-temporal optimisation framework, which considers soil in a time-dependent resource extraction perspective. This thesis has demonstrated that soil degradation is causing an enormous reduction in the productive value of smallholder land in Malawi. Current user cost of soil quality based on current practices of smallholder farmers, which represents annual loss in productive value of land, was estimated to be US$21 per hectare. Based on this value and land area under smallholder agriculture in Malawi, economic costs of soil degradation among smallholder farmers were estimated to amount to 14 per cent of the agricultural GDP. If left unabated, soil degradation threatens not only the future of smallholder agriculture but also, economic growth prospects of the nation. Although not operating on the SS optimal path in terms of soil resource management, current practices show that smallholder farmers in Malawi still consider, to certain degree, the dynamic costs in soil resource use. Hence, there is no strong evidence to suggest that current trends in land degradation are due to an institution failure (i.e., smallholder farmers have private incentives to conserve their soil resource). A result that suggests presence of other factors, most likely market distortions, behind existing deviations of farmers' practices from dynamic optimum. Government's serious support of the input and output market reforms is important not only to make the markets work but also, to make smallholder agriculture a profitable enterprise. It is only when smallholder agriculture becomes profitable that farmers can seriously invest in the soil resource. Agricultural support programs such as "food for work" if extended to include soil conservation, could lead to substantial curtailment of soil erosion since farmers can invest their labour in their own gardens during the critical times of land preparation. The sensitivity analysis indicated that increasing the discount rate to' 5%, SS solutions were close to current practice solutions. This suggests that one reason smallholder farmers are exploiting the soil resource is because they have a higher time preference. The high levels of poverty, especially among the smallholder subsistence farmers in Malawi, entail that farming households are more concerned with their survival now than their future well being. The study estimated an optimal output of 1.5tonlha and nitrogen fertiliser rate of 49 kg/ha at SS. The fertiliser estimates are based on smallholder farming system that incorporates soil conservation. In one of the most detailed studies on nitrogen use efficiency in Malawi, Itimu (1997) indicated that with the incorporation of manure, nitrogen fertiliser use dropped from 60 to 30 kg/ha to produce about 2.5 tons of maize. Malawi uses area specific recommendations for fertiliser application. However, using "best bet" technologies, at least 35kgN/ha is recommended for smallholder farmers on average. The SS optimum fertiliser estimated in the current study was somehow higher due to the fact that an inter-temporal framework, which considered the dynamic costs of soil nutrient extraction, was used. Results from fertiliser recommendation trials may be reinforced if researchers consider the inter-temporal nature and dynamic costs associated with the use of soil. The selective tobit model results indicate that factors that influence smallholder farmers' decisions to adopt soil conservation technologies may not necessarily be the same factors that influence subsequent decision on levels of adoption. The implication of this finding is that different policy prescriptions on soil conservation should strictly be guided by the goals the government wants to achieve. With fertiliser prices being out of the reach of most smallholder farmers in Malawi, soil conservation is one of the reliable options available to reduce soil degradation. However, any policy aimed at improving adoption of soil conservation technologies among smallholder farmers would succeed only if the various needs of smallholder farmers at the two decision stages are properly identified and addressed. / Thesis (PhD (Agricultural Economics))--University of Pretoria, 2006. / Agricultural Economics, Extension and Rural Development / unrestricted

Mega-events are associated with significant positive implications such as enhanced international exposure of the host, improved infrastructure, increased tourist numbers, higher employment levels and tax revenues, greater feelings of patriotism among host region residents and integration of the host into the international community. Supporters of events have claimed that the occasions stimulate prominent economic gains for the host region. The economic and tourism growth that occurred in Barcelona following the 1992 Olympic Games is erroneously cited by proponents of hosting as an example of the potential benefits that an event can derive on the host. Those Games were not the sole driver of growth in the region. An analysis of previous mega-events, demonstrated that net benefits were not a necessary consequence of hosting. Comparison of pre-event estimates of the economic impact and their actual effects are universally divergent. The observation was validated by the consensus academic opinion that economic impact studies systematically overstate the benefits of hosting, and underestimate the costs. Further, different forward-looking studies of the same event, calculate vastly different predictions. The tools for calculating the economic impact, specifically Input-Output Analysis and Computable General Equilibrium, do not provide useful predictions given their dependence on the inaccurate data. With 2010 cost data having continually increased since 2003, determining the appropriate inputs to an I-O or CGE is problematic. It was identified that the weight given to the multiplier effect was also a factor in the amplification of the expected benefits. Given the poor data sets available as inputs to I-O and CGE models, the study concentrated on conducting a comprehensive Cost-Benefit Analysis of the determinants of the economic impact of the 2010 World Cup based on the premise that the identification of the relative costs and benefits of staging the event was regarded as a greater contribution to the body of knowledge on the topic. It can be expected that there will not be significant short-term economic gains; this study predicted a net cost of R8.4bn, which is marginally offset by short-term net intangible benefits. The short-term economic consequences of the 2010 World Cup are expected to be overshadowed by the long-term effects on revenues within the tourism industry. The image implication of hosting 2010 is the most salient factor in considering the economic impact of 2010, as an alteration in the national image can have long-term effects on FDI and tourism. It is however not a certainty that the international exposure that South Africa receives will be beneficial, in the instance that the World Cup is characterised by poor organisational measures or crime. The net impact of hosting is expected to be a function of the long-term benefits, which can be expected to exceed the short-terms costs, and derive a cumulative net benefit from staging 2010. The World Cup is however unlikely to stimulate the economic growth rate above levels that would have occurred had the event not been held in South Africa.

In the first chapter, I measure the effects of street-level political advertising on voting behavior. I use a novel dataset on ad location in a major Spanish city during elections for the national parliament as well as granular socio-economic and voting data. This set-up, where more than two parties are running for office and elections are very competitive, allows me to explore the heterogeneous effects of ads across parties as well as how parties' ads affect other parties' vote shares. To identify the effects of parties' ads, I exploit a legally mandated randomized assignment of ad location to parties across multiple years. I find that a party's own ads have a positive effect on its vote share, although the effects are heterogeneous across parties. A one standard deviation increase in the number of ads increases a party's vote share by 0.79 percentage points on average. Ads of parties with ideologically distant platforms consistently have a negative effect on a party's vote share. In contrast, ads of parties that are close competitors may act either as complements or substitutes in different years. The second chapter analyses the effects of an economic shock on the emergence of new parties and other changes in voting parties by using regional variation in the exposure to the shock. I find that a worsening of economic conditions as measured by unemployment rate leads to an increase in electoral competition and volatility. In particular, the deeper the effects of the recession in a area, the larger the number of new parties emerge and become more successful and there is an increase in the changes in vote shares. On the other hand, the vote share of parties previously in government decreases and a decrease in vote share concentration. The third chapter is a co-authored works where we present experimental evidence establishing that the level of incentives affects both gameplay and beliefs. Holding fixed the actions of the other player, we find that, in the context of dominance-solvable games, higher incentives make subjects more likely to best-respond to their beliefs. Moreover, higher incentives result in more responsive beliefs but not necessarily less biased. We provide evidence that incentives affect effort and that it is effort, and not incentives directly, that accounts for the changes in belief formation. The results support models where, in addition to choice mistakes, players exhibit costly attention.

With many genetic traits discovered and many more in progress, it is imperative to the industry that firms (biotechnology companies) decide on the trait valuation and pricing. This includes more than one trait (also referred to as stacked traits) in a single variety of crop; the risk and uncertainty of expected returns associated with the development and release of a variety increases even more in case of stacked traits. The purpose of this thesis is to develop a model that can be used for the valuing and pricing of genetically modified (GM) traits that are random, sporadic, and non-persistent (e.g. drought tolerance, heat/cold stress) using the real option approach. The efficiency gain in case of occurrence of random event and expression of GM traits will be measured and used as a decision factor in determining the value of GM trait(s) at different phases of development. Risk premiums representing the value of GM trait to growers is calculated across risk averse attitudes. The return to labor and management (RTLM) provided by a GM trait is used to calculate the risk premiums when variation in parameters is allowed to be same as that reflected in historical data and gains from GM traits are realized. Monte Carlo simulation and stochastic efficiency with respect to a function (SERF) are used to estimate the certainty equivalents that decision makers would place on a risky alternative relative to a no risk investment. Certainty equivalents are estimated across a range of risk aversion coefficients and used to rank alternatives and determine where preferences among alternatives change while estimating risk premiums for the base case (no trait), drought tolerance, cold tolerance, NUB, and All traits (all traits combined into one as a stacked trait). Premiums provide perspective on the magnitude of differences in relative preferences among choices. The range of ARAC utilized was from 0.00 to 0.15 for all three crops. The risk premiums are treated as a potential source of revenue in the model as a technology fee charged by a biotech company. This thesis uses the Real Option methodology to evaluate GM traits as Option values at various stages of development. This approach helps managers decide the best possible option in making a certain decision today. It is also helpful in comparing different pathways (series of decisions) and thus better exploits the potential cash return in the future from investments made today (Figure D.1, Figure D.2). Three possible options to "continue", "wait", and "abandon" were modeled in this thesis. Such modeling determines the possible option values of GM traits at different stages of development depending on the kind of choices made at different points of time. This thesis shows that various GM traits that are out-of-money (OTM) at initial stages have increased probability of being in-the-money (ITM) at later stages of development. Sensitivities show that a share of potential technology fees and acreage of GM crops play a significant role in option values being ITM. Stacked traits provide a better chance of being ITM, thus the option to continue will be exercised by management. The option to wait causes reduction in option value. Among individual traits, drought tolerance has the greatest maximum option value in most cases. Therefore, if management has to choose the development of only one GM trait, it is most likely to choose to invest in the development of drought tolerance.

In the first chapter of this dissertation, I exploit the Covid-19 pandemic and associated government restrictions as a natural experiment in order to study the resilience of businesses in the United States. I use a border-county identification strategy with data on government restrictions, employment and open small businesses, in order to assess the resilience of small businesses in the United States. In my main results, I find negative impacts of stay-at-home orders on the number of open small merchants. In particular, shutdowns of businesses accelerated 8 weeks after imposition of a stay-at-home order, suggesting that many businesses were only resilient enough to handle adverse conditions for 8 weeks. On average, a county with a stay-at-home order experienced an additional 1.51 percentage points loss in the number of open small businesses, relative to January 2020, 8 weeks later compared to a neighboring county that did not have a stay-at-home order. Firms were quicker to resort to layoffs. On average a county with an active stay at home order in a month experienced an additional 1.19 percentage point loss in employment, relative to January 2020, the following month compared to a neighbor that did not have a stay-at-home order the previous month. My results suggest that in future scenarios where governments consider enacting similar restrictions further aid is needed for businesses in order to help them stay afloat. In particular, more assistance should be delivered to businesses within two months from the enacting of the order. In the second chapter of this dissertation, I study economic spillovers in the context of theCovid-19 associated government restrictions. I use a detailed geolocation dataset to construct data on the number of visitors per-capita between neighboring counties in the early stages of the pandemic, which I use as a proxy for economic spillovers. I employ a similar border-county identification strategy as in the first chapter to identify the causal effect of stay-at-home orders on inter-county movement. Additionally, I provide evidence for an assumption used in chapter one by examining if there are reduced spillovers in county-pairs that lie in the different commute zones. I find that stay-at-home orders caused reductions in inter-county visits in both directions in a county-pair. That is, I find a decrease in travel from the county without a stay-at-home order to the county with one, as well as a decrease in the opposite direction. On average, a county that does not have stay-at-home order will receive 408 fewer weekly visitors from their neighboring county that has a stay-at-home order. I also examine the effect of stay-at-home orders on the ratio of travel between the two directions in order to find evidence of a net spillover effect between the two counties and fail to find evidence of a net spillover effect. I also find that spillover effects are indeed reduced in neighbor county-pairs where the two counties are in different commute zones. The results of this paper imply that residents in counties with stay-at-home orders decreased travel to their neighboring counties even when those counties did not issue their own orders. In future situations where policy makers need to consider similar restrictions, they should focus on acting more quickly and not be concerned if neighboring counties are not cooperative. In the third chapter of this dissertation, I test the predictions of career concerns models by studying Major League Baseball umpires. Major League Baseball games can be dramatically shaped by minor lapses in judgement from the umpires officiating the game. Due to the indefinite length a game may have, this can include having the game shaped in a way that ends it faster. I study whether evidence for the career concerns model can be found in baseball umpires. A career concerns model would suggest that older umpires, whose careers and reputations are much more established than younger ones, would be more inclined to improperly make judgements that favor the end of the game in extra innings. I use data on MLB umpires and extra-innings games from the 2010-2018 seasons to conduct my empirical analysis and use a linear probability model to isolate the impact of the umpires’ tenure on the probability they make a “bad call.” I find evidence supporting the career concerns hypothesis and that the probability that an umpire makes a bad call that shortens the length of the game and allows them to go home increases with their tenure. I show that these results are likely driven by career concerns, rather than carelessness, by showing their error rate does not increase with tenure in situations where it would not reduce their workload.

Tang Lok Ming. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 86-87). / Abstracts in English and Chinese. / Chapter 1. --- Introduction --- p.1 / Chapter 2. --- Severe Acute Respiratory Syndrome (SARS) --- p.8 / Chapter 2.1 --- Nature of SARS --- p.8 / Chapter 2.2 --- Impacts of SARS --- p.9 / Chapter 2.3 --- Literature of SARS --- p.13 / Chapter 2.4 --- Evolution of SARS in Mainland China --- p.16 / Chapter 3. --- Event Study Methodology --- p.18 / Chapter 4. --- Data --- p.24 / Chapter 5. --- Results --- p.25 / Chapter 5.1 --- Hong Kong --- p.26 / Chapter 5.2 --- Mainland China --- p.31 / Chapter 6. --- Conclusion --- p.47 / Figures --- p.50 / Tables --- p.59 / Appendix --- p.64 / References --- p.86

published_or_final_version / Transport Policy and Planning / Master / Master of Arts

published_or_final_version / Urban Planning / Master / Master of Science in Urban Planning