The US innovation system has many strengths, including world class research universities and firms that thrive in innovation-intensive sectors. However, fissures have begun to appear, notably in the areas of human capital development, the patent system and manufacturing activity, while public investments in R&D and research universities are at risk of being curtailed by budget cuts. Revitalizing the dynamism of innovation has become a priority for US policymakers. To this end, it is important that federal and state governments sustain financial support for knowledge creation. The US workforce’s skills will need to be upgraded, especially in STEM fields, and measures taken to provide more favourable framework conditions for developing advanced manufacturing in the United States. While the recent patent reform is a big step in the right direction, patent reform needs to be taken further by ensuring that the legal standards for granting injunctive relief and damages awards for patent infringement reflect realistic business practices and the relative contributions of patented components of complex technologies. Renforcer l'innovation aux États Unis Le système d’innovation des États-Unis possède de nombreux atouts, en particulier des universités de recherche de rang mondial et des entreprises dynamiques dans les secteurs à forte intensité d’innovation. Cependant, certaines failles commencent à apparaître, notamment en termes de formation du capital humain, de brevets et d’activité manufacturière, et les investissements publics en faveur de la R-D et des universités de recherche risquent de pâtir des réductions budgétaires. Pour les décideurs américains, réactiver la dynamique de l’innovation est devenu une priorité. À cette fin, il importe que le gouvernement fédéral et les exécutifs des États continuent de soutenir financièrement la création de connaissances. Il faudrait améliorer le niveau de qualification de la main-d’oeuvre, en particulier dans le domaine des sciences, de la technologie, de l’ingénierie et des mathématiques (STIM), et prendre des mesures pour assurer la mise en place de conditions-cadres plus favorables au développement de la fabrication de pointe. La récente réforme des brevets représente un grand pas dans la bonne direction, mais elle doit être poursuivie en garantissant qu’en cas d’atteinte à un brevet, les critères juridiques sur lesquels se fondent les tribunaux pour prendre des décisions conservatoires et accorder des dommages-intérêts reflètent les pratiques effectives des entreprises et les contributions relatives des composantes brevetées des technologies complexes.

This study investigates how the 1996 welfare reform legislation, the United States Personal Responsibility and Work Opportunity Reconciliation Act (PRWORA), impacted poverty and workforce participation outcomes for immigrants in the United States. Among other new restrictions for all individuals in the United States, PRWORA removed welfare eligibility for non-citizens for their first five years in the country and instituted work requirements for all citizens to receive welfare. This study uses a triple-difference linear probability model similar to Borjas (2003) to measure changes in the likelihood of being in poverty and participating in the workforce by citizenship status, state provision of welfare, and time. Results are calculated for two post-PRWORA time periods, 1998- 1999 and 2008-2009, and compared to the pre-PRWORA time period 1994-1995. PRWORA is found to have increased the likelihood of being in poverty for non-citizens with children living in states not providing welfare to immigrants in the second post- PRWORA period. In states that chose not to provide welfare to immigrants, PRWORA increased the likelihood that naturalized citizens participate in the workforce in the first post-PRWORA period but decreased the likelihood that non-citizens in those states participated in the workforce in the second post-PRWORA period. These findings suggest that PRWORA negatively affected immigrants as a group, particularly non- citizens, and that the five-year bar on eligibility for welfare should be removed. I want to thank my thesis advisor for all his patience, encouragement, and guidance throughout this process. I also want to thank my family and friends for their support and listening ear when I was not sure how I would get it all done. Most of all I want to thank Patrick, the love of my life, for giving up so much to make pursuing this degree possible.

This paper proposes a manipulation language tailored for OLAP query logs, stemming from the relational algebra. This language is based on binary relations over sequences of queries (called sessions). We propose two such relations allowing to group and order sessions. Examples of expressions in this language illustrate its interest for various user-centric approaches, like query recommendation or log summarization, particularly relevant in the context of data warehouse exploration.

A science of cities and regions seeks an in-depth understanding of their workings and how they evolve over time. This is not only interesting as science, but is also potentially useful in a variety of planning contexts. In common with many other sciences, mathematical modelling provides a valuable approach. There is a history of 50 years or more of serious development and therefore a substantial body of literature and ideas.

The well-being of immigrant youth - of the first or second generation - is intimately tied to their socioeconomic status and success, and these are important for social cohesion in society. Institutional settings and policies vary greatly from one country to the next, so studying key outcomes for immigrant youth in a comparative perspective illuminates which are most effective in promoting their well-being. In this chapter, a framework is presented for that exercise, highlighting recent literature on multidimensional well-being, social inclusion/exclusion, and child well-being. Then key findings from research on immigration and youth are examined within that framework in order to delineate the potential and the challeneges associated with this approah to teasing out what works for immigrant youth.

Sorting models to date have operated at the macro level or micro level. Regardless of the scale, all existing sorting models analyze a single choice from a single set of alternatives. Intu- ition suggests, however, that households choose a city and subsequently select a neighborhood within that city. This stylized reality is absent from conventional sorting models, which ignore information at one of these stages. In addition, due to the size of the full choice set, capturing this entire sorting process in a single model can be prohibitive in terms of computation and data collection. I use the theory of two-stage budgeting to develop an empirically feasible sorting model that more accurately replicates household behavior. Empirically, I focus on the cost of air pollution. Results point to an additional tradeoff between air pollution and neighborhood- level amenities that increases the marginal willingness to pay for clean air by a considerable amount. I also show that allowing for heterogeneity in preferences for local public goods has a considerable impact on the estimated value of clean air. This dissertation also explores an application of the model in which I construct spatially explicit measures of the cost of living that can be used to adjust income and calculate a broad measure of welfare. The analysis focuses on the distribution of such welfare across the popu- lation, as well the change in this distribution followings simulated reductions pollution concen- trations. Empirical results suggest that accounting for public goods leads to a distribution of adjusted income that has a wider spread than that of pure monetary income. This implies that households with less income tend to face higher costs of living, determined by an inferior set of public goods relative to housing prices paid to obtain such goods.

This paper examines the implicit health insurance households receive from the ability to declare bankruptcy. Exploiting cross-state and within-state variation in asset exemption law, I show that uninsured households with greater seizable assets make higher out-of-pocket medical payments, conditional on the amount of care received. In turn, I find that households with greater wealth-at-risk are more likely to hold health insurance. The implicit insurance from bankruptcy distorts the insurance coverage decision. Using a microsimulation model, I calculate that the optimal Pigovian penalties are similar on average to the penalties under the Affordable Care Act (ACA).

Although the ADA was passed in 1990 to address, in large part, the decreasing employment rate and economic wellbeing of persons with disabilities - twenty-years later - the trend has not reversed. We identify five main arguments that have been offered in the literature as to why this is the case. They are: (1) the unintended consequences argument, (2) the judicial resistance argument, (3) the capitalist structure argument, (4) the attitudes and norms argument, and (5) the welfare and government benefits argument. Drawing from these arguments, we analyze pooled Current Population Survey data from 1992 through 2010 using multilevel varying-intercept models. We find that indeed, employment conditions for persons with disabilities have actually worsened since the ADA was passed. In addition, employed persons with disabilities have seen very little change in earnings, even after controlling for differences in demographic and education variables. We also find that in states that did not pass their own ADA-like legislation, the employment rate for people with disabilities was about 5 percentage points lower as were disability earnings. We find ambiguous results with regards to the relationship between EEOC charges and employment suggesting that the effects of fear of persecution on employment is not that clear cut. These findings suggest that ADA-like laws may not be producing unintended consequences. We do, however find support for our fifth explanation related to state spending on benefits for the disabled population, where increases in spending results in potential disincentives for employment.

Better contraception will have competing impacts on marital stability and divorce rates. Preexisting marriages are likely to become less stable as better contraception raises the value of reentering the dating market. Subsequent marriages are likely to be more stable as couples delay marriages and use better contraception to search for better partners. I investigate this hypothesis using variation in access to the birth control pill by state and cohort as developed by Goldin and Katz (2002). Access to the pill decreased stability of preexisting marriages and increased stability of subsequent marriages. * I thank Derek Neal and Emily Oster for many helpful comments. All mistakes are my own. Any and all comments welcome.

A system and method of identifying relational patterns across a plurality of databases using a data structure and the data structure itself. The data structure including one or more data node branches, each of the one or more data node branches including one or more data nodes, each of the one or more data nodes representing a data item of interest and corresponding data item support values for the data item across the plurality of databases in relation to other data items represented in the data node branch. The data structure can be used to mine one or more relational patterns considering pattern support data across the plurality of databases at the same time.

The Social Security Disability Insurance (DI) Program, which provides income protection to qualified workers who suffer from disabilities, is now facing rapid growth in the number of recipients. The DI program also discourages exit by workers whose health improves by penalizing work heavily. In the first chapter, I build a dynamic general equilibrium model to provide a quantitative analysis of the welfare effects of the DI program and the impact of DI policy reforms on the program's financial health and on worker behavior and welfare. A recently proposed policy to provide two extra years of partial benefits for DI beneficiaries returning to work would reduce the size of the DI beneficiary population, lowering total DI payments and the tax rate and raising welfare of a healthy newborn by 0.33%. Increasing the Social Security Normal Retirement Age from 65 to 67 raises the number of DI recipients by 8.9%. Policy changes strengthening the strictness of disability criteria increase social welfare mainly due to the reduction in the tax rate. Lastly, simulation results for the case of eliminating the DI program shows a large welfare gain in the new steady state, implying that the distortionary effects of taxation outweigh the gains from providing insurance. The second chapter takes into consideration that people can also obtain financial protection from public and private health insurance programs to have medical costs covered when they suffer health problems. I build a dynamic general equilibrium model to quantitatively analyze the impact of policy reforms on the DI program and on workers' behavior and welfare when Medicare, Medicaid, and employer-sponsored health insurance programs interact with the DI program. A policy change strengthening the strictness of the DI admission process increases social welfare mainly due to the reduction in the tax rate and the increase in the wage level. Expanding Medicaid eligibility, which is a provision in the Affordable Care Act, reduces the number of DI recipients by 4.0% and increases general equilibrium welfare by 0.1%. However, the welfare effects differ by education.

African Americans increasingly are moving from inner cities and inner-ring suburbs to fast-growing exurbs on the urban fringe, trends that media reports attribute primarily to their desire to live affordably as homeowners in safer communities. Little empirical evidence exists to support these claims, although research on the drivers of postwar black suburbanization and a burgeoning exurban migration literature suggest that desires for ownership and housing space, to escape inner-city poverty concentration, and to create "places of their own" may be contributing factors. Through interviews with 70 African Americans who moved from Los Angeles County to its fast growing exurban Inland Empire between 1980 and 2010, this research shows how race- and context-specific factors, such as affordable housing shortages, gang violence, and Latino occupancy of historically black communities, are contributing to black population growth on the urban fringe.

Decades of research on the US gender gap in wages describes its correlates, but little is known about why women changed their career paths in the 1960s and 1970s. This paper explores the role of "the Pill" in altering women's human capital investments and its ultimate implications for life-cycle wages. Using state-by-birthcohort variation in legal access, we show that younger access to the Pill conferred an 8 percent hourly wage premium by age 50. Our estimates imply that the Pill can account for 10 percent of the convergence of the gender gap in the 1980s and 30 percent in the 1990s.

In 2006, Massachusetts passed a health care reform which required individuals to purchase health insurance and provided subsidized health insurance to the poor. The reform greatly increased the proportion of the state population that was insured. In this study we use a large data set of private health insurance claims to analyze the effect of the increase in the number of insured on the price of care. Findings of note are that prices for well-infant visits rose by approximately 7 percent, whereas prices for well-adult visits rose by approximately 3 percent. The price of appendectomies, for which price elasticity of demand is inelastic, remained unchanged. Triple difference estimates using appendectomies as an additional control group show a 6 percent rise in well-infant visit prices and no effect on well-adult visit prices. Our estimates imply a large increase in the cost of health services with relatively elastic demand (such as well-adult visits) following a large scale insurance mandate such as the Affordable Care Act.

American cities have proliferated in the post-War era. More than 2,000 new citieswere founded between 1950 and 2000. While the history of the local government boomhas been documented, research into urban fragmentation has explored why there is noconsolidation of metropolitan areas rather than exploring why Americans chosefragmentation initially.This dissertation proposes that individuals create new jurisdictions becauseindividuals prefer to have governments which give them the services individuals desire,even if they could have similar (but not perfect) services cheaper in a larger jurisdiction.

A wealth of data drawn from cities and their nearby suburbs show that, consistent with place stratification theory, African Americans live in poorer quality communities than similarly affluent members of other racial groups. Yet, few have examined whether these trends are playing out in the rapidly growing exurbs, places that emerged in the post-Civil Rights era. Through a case study of African American migration to Los Angeless exurban Inland Empire, this article tests the applicability of place stratification theory by triangulating evidence from interviews with 70 movers with U.S. Census and American Community Survey data. Both sources reveal that the gap in neighborhood conditions among similar income racial groups is much narrower in the exurbs than inner city Los Angeles or its nearby suburbs, an outcome that participants attributed to the regions rapid housing construction, relative lack of a history of who lives where, and resulting neighborhood diversity.

High school graduates from low-income families are much less likely to attend and complete college. Financial assistance is a major policy lever to influence their educational choices. However, there is mixed evidence regarding its effects on low-income students. In this paper, I estimate the effects of student subsidies, student loan access, and family income transfers on college attendance and completion. I use an Instrumental Variables approach based on a large set of laws involving Guaranteed Student Loans, Pell Grants, Aid to Families with Dependent Children, and Social Security. These laws treated different families in different ways, based on family structure, size, state and income. I have three main findings. First, using policy variation in the Pell, AFDC and Social Security student benefit programs, I find that attendance changes by 1.0 - 1.2 percentage points per $1000 in annual student subsidies, which is considerably below the conclusions of prior literature reviews. I do not find significantly different effects across programs or subgroups. I find a smaller effect of subsidies on college completion. I estimate that these programs spent about $40,000 per student induced to attend, as most recipients would have attended anyway. Second, using state-by-year variation in the introduction of Guaranteed Student Loan programs, I do not find an effect of student loan access on overall attendance or on attendance of low-income students. Third, I find an insignificant effect of family AFDC and Social Security income on attendance.

The role of human capital in economic growth is now largely uncontested. One indicator of human capital frequently used for the pre-1900 period is age heaping, which has been increasingly used to measure gender-specific differences. In this note, we find that in some historical samples, married women heap significantly less than unmarried women. This is still true after correcting for possible selection effects. A possible explanation is that a percentage of women adapted their ages to that of their husbands, hence biasing the Whipple index. We find the same effect to a lesser extent for men. Since this bias differs over time and across countries, a consistent comparison of female age heaping should be made by focusing on unmarried women.