Where are the facts for spending on a WALL?

In the pursuit of providing sources of information that can be used as an alternative to consumption of news and opinion sources, here is a great site to better understand the data associated with migration. The Mexican Migration Project is a significant set of facts and data around the issue / opportunity of migration.  Found this after listening to Malcolm Gladwell's Revisionist History this week. Learned from that podcast that the wall is actually keeping migrants here. (also learned that there are no published biographies of General Leonard Chapman which was disappointing.) Just spend 30 minutes looking at the results. My takeaway: over the last 8-10 years we have more than doubled the cost of a border crossing and reduced the probability of an undocumented Mexican crossing the border for the first time by 0.0135. That seems like an unwise investment.