Chapter 1: High-skilled migration and higher-education attainment rose globally in the period between 2000 and 2010. These trends raise the question of whether increases in higher-education attainment led to increases in high-skilled emigration in source countries during this period? To the contrary, I found a strong negative correlation between percentage changes of high-skilled emigration rates and percentage changes of high-skilled proportions in non-OECD countries. Using the IAB Brain Drain, Barro-Lee and World Development Indicators Datasets, I estimated the elasticity of high-skilled emigration rates with respect to high-skilled percentages in non-OECD countries with ordinary least square, least absolute shrinkage and selection operator (LASSO) and post-double-selection LASSO. The estimates ranged between -0.78 and -0.98. Chapter 2: In 2015, the state of Georgia eliminated exit exams from high school graduation requirements in an education reform. I study this reform's impact on 4-year high school graduation rate, post-secondary institutions enrollment and employment rate among new high school graduates. Using the state of Florida as control, I estimate weighted difference-in-difference analyses at the school level for graduation rates and at the district level for post-secondary institutions enrollment and employment rates. The reform increased graduation rate by 4% for all students, and by 1.4% for White, 5.98% for Black and 5.59% for Hispanic subgroups. The reform decreased post-secondary institutions enrollment rate by 1.8% but had no statistically significant impact on employment rate among new high school graduates who don't pursue post-secondary education. In the pre-periods, the trends are parallel for graduation rates, post-secondary institutions enrollment rates and employment rates between Georgia and Florida. I conclude that although exit exams elimination increased 4-year graduation rates (especially among Black and Hispanic students), the additional diploma holders are less likely to enroll in post-secondary institutions and no more likely to be employed when choosing not to pursue postsecondary education. Chapter 3: I propose a new semi-parametric estimator for the Tobit Type-3 sample selection model. I first generalize the mode regression estimator to its bivariate counterpart. I then apply this bivariate mode regression estimator to the Tobit Type-3 model under two separate sets of assumptions. First set will be computationally simpler but requires more restrictive assumptions, while second set will be more computationally taxing yet requires less restrictive assumptions. I then show that the estimators are identified and strongly consistent under both sets of assumptions.