In the latest edition of the Cato Journal, economist Bryan Roberts argues that immigration enforcement has significantly diminished the flow of illegal immigrants across the Southwest border. Contra Roberts, sociologist Doug Massey argues that border enforcement had virtually no impact on the flow of unlawful immigrants prior to 2010. This post takes a slightly different approach and uses additional sources of data to look at the causes behind the decline of illegal immigration in the aftermath of the Great Recession. This is especially relevant as the House Judiciary Committee is marking up the Agricultural Guest Worker Act (Ag Act) that would increase the flow of temporary visas for workers in farming and related sectors. An increase in visas like those supplied by the Ag Act will likely further diminish unauthorized border crossings.
Model and Data
This blog is intended to reveal whether the quantity of Mexican legal immigrants (green cards issued overseas and temporary migrants) or border security is responsible for the decline of illegal immigrants from Mexico. Our dependent variable is the estimated gross annual flow of Mexican illegal immigrants. The American unemployment rate, the difference between Mexican and American GDP per capita (PPP), line-watch hours at the Southwest border, and legal Mexican immigration are our independent variables.
We chose a log-linear OLS model to compensate for non-linearity. OLS is a type of regression that helps identify the relationship between independent variables that we anticipate will explain how dependent variables behave. We then ran an autoregressive model (AR (1)) that will help us account for a particular empirical anomaly, the serial dependence between current and immediate past variables that could affect an OLS regression. We then ran a series of regressions with the yearly aggregates beginning in 1960 and ending in 2009. Data limitations prevented us from going beyond 2009 and prior to 1960.