Societies frequently implement land use policies to regulate resource extraction or to regulate development. However, two important policy questions remain unresolved. First, how effective are land use regulations? Second, how do land use regulations affect socioeconomic conditions? Three issues complicate the evaluation of land use policies: (1) overt bias may lead to incorrect estimates of policy effects if implementation is nonrandom; (2) the policy may affect outcomes in neighboring unregulated lands; and (3) unobservable differences between regulated and unregulated lands may lead to biased assessments. Previous evaluations of land use policies fail to address these sources of bias simultaneously. In this dissertation, I develop an approach, using matching methods, which jointly accounts for these complications. I apply the approach to evaluate the effects of Costa Rica s protected areas on land use and socioeconomic outcomes between 1960 and 2000. I find that: (1) protection prevented the deforestation of only 10 percent or less of protected forests; (2) protection resulted in reforestation of only 20 percent of non-forest areas that were protected; (3) protection had little effect on land use outside protected areas, most likely because, as noted above, protected areas had only small effects on land use inside protected areas; and (4) there is little evidence that protected areas had harmful impacts on the livelihoods of local communities: on the contrary, I find that protection had small positive effects on socioeconomic outcomes. Furthermore, the methods traditionally used to conduct such evaluations are biased. In contrast to the findings above, those conventional methods overestimated the amount of avoided deforestation and erroneously implied that protection had negative impacts on the livelihoods of local communities. This dissertation contributes to policymaking by providing empirical measures of protected area effectiveness. Although annual global expenditures on protected areas are about $6.5 billion, little is known to date about the returns on these investments. This study also indicates that policymakers should give careful consideration to current proposals to compensate communities living in or around protected areas: contrary to widely held assumptions, the findings suggest that protection may not have harmful effects on socioeconomic outcomes. Advisors/Committee Members: Paul J. Ferraro (Committee Chair), Alex Pfaff (Committee Member), Douglas Noonan (Committee Member), Gary T. Henry (Committee Member), Gregory B. Lewis (Committee Member).