In 2009, in the wake of rapid inflation, Chinese unit labor costs were 72% of Mexico’s. (See page 19 at the link.) By early 2010, Chinese unit labor costs had risen to 86% of the Mexican level, and Mexico started to export cars to China. For some goods, landed costs (i.e., the cost of manufacturing and moving to the mainland U.S.) are much cheaper in Mexico than in China.
If you only look at the Chinese side, there seems little prospect of these trends turning around. China is experiencing bad labor shortages. Moreover, China has an inflation problem (the strategies described in this post seem to be hitting their limit) and its low inflation of 3% is not much lower than Mexico’s higher-than-expected 3.9%. Meanwhile, the peso is falling, while the yuan is likely to head nowhere but up. (If that turns out to be wrong, expect bad political consequences.)
On the other hand, if you look at the Mexican side, the reason Mexico is gaining competitiveness is that wages are flat. And flat at a low level. The good news is that Mexico is seeing rapid employment growth (see chart below) but Mexico no longer has endless millions of peasants to pull into the cities. Job growth is a good thing, of course, but it can go only go on for so long. (Mexico rebased its employment measures in 2010; thus the two indices.)
Translation: this is good news for Mexico, but it is a one-time thing. Without productivity growth, either within industries or by shifting into new products, Mexico wll remain relatively poor.
Implication: if the U.S. economy ever picks up again, so will emigration.
Omission: the effect of violence and extortion. The jury is out.