But this report argues persuasively that the main reason for the drop is something else -- the huge improvement in opportunities and standard of living within Mexico itself.
To begin with, secularism has reduced the influence of the Catholic Church, leading to rising use of contraception and a falling birth rate (in 1970 it was 6.8 children per woman -- it is now 2 children per woman). This improves the standard of living since there are fewer dependents per worker.
Mexico's government has invested in education, improving the country's schools. Enrollment in secondary and higher education has increased much faster than population growth. This is critical for sustaining growth over the long term, since a more educated work force is more productive.
Mexico's GDP per capita and family income have risen more than 45% since 2000.
It's deep changes in society like these, rather than the ephemeral initiatives or statements of this or that politician or party, that drive genuine progress.
None of this should be surprising. We're used to hearing that other large Third World countries such as India, China, and Brazil have launched the kinds of economic and social transformations that will ultimately enable them to catch up with the developed world, and are already narrowing the gap. Why shouldn't Mexico be doing the same?
American perceptions of Mexico tend to be dominated by the drug-cartel violence afflicting the country, and indeed we have no business neglecting that issue, since it's largely our own insane drug-prohibition laws that fuel and fund the violence. But that's not the only, nor the most important, thing happening in Mexico.