In the American immigration debate, the point is often made on talk radio that Mexicans stream into the United States because their birth rate is so high. Mainstream sources sometimes make the same argument. In June, 2010, Britain’s Prince Charles warnedabout the “cultural pressures that keep the global birth rate high,” arguing that the same is true in “Mumbai, Cairo or Mexico City; wherever you look, the world’s population is increasing fast.”
The population of Mexico City is certainly increasing, but not because the country’s birth rate is elevated. Mexico’s total fertility rate (TFR), or the number of children born to an average woman, is actually very close to 2.1—essentially the same as that of the United States. If Mexico’s population continues to expand, it is because its fertility drop is so recent. At its current birth rate, the Mexican population will soon stabilize even without emigration to the United States. As a developing country, Mexico is hardly alone in this situation. Mauritius’s TFR is 1.9, Thailand’s is 1.8, and Trinidad and Tobago’s is 1.6, all well below replacement level.
In Mexico, fertility patterns vary significantly from state to state, as is to be expected. The map that I have constructed above using demographic data from the 2000 census shows a distinct regional pattern, with relatively high fertility rates in the south contrasting sharply with lower rates in both the north and center (including greater Mexico City). The correlation with socio-economic development is marked, as is made clear by comparing this map with that of Mexico’s Human Development Index. But even Mexico’s least developed states have relatively low birth rates by historical and global standards, with only Guerrero exceeding 3.0 in 2000.
Urbanization as well as development correlates with reduced fertility. Consider the state of Mexico, the country’s most populous political subdivision, with more than 14 million inhabitants. This state encompasses many of the poorer parts of Greater Mexico City, and thus has a per capita level of economic output substantially lower the national average ($8,900 for the country of Mexico vs. $6,200 for the state of Mexico, in nominal GDP). Yet the state’s birthrate is well below the national average, having been under the replacement level even in 2000. The state of Mexico also sends a disproportionate number of emigrants to the United States, “making up about 75.7% of the total Mexican population that migrates,”according to the unsupported figures given in the Wikipedia. (Intriguingly, Mexican-Americans have significantly higher birth rates than Mexicans. In 2007, Hispanics in general in the United States had a TFR of 2.9 in 2007, as compared to 2.1 for blacks, 1.9 for Asians, and 1.86 for whites.)
At the global scale as well, Prince Charles’s insinuation that contemporary urban surges in the Third World result from elevated birthrates is misleading. Cities have fed on migration from the countryside since the dawn of urbanization 5,000 years ago; before the 1800s, death rates in urban areas almost always exceeded birth rates. Although modern methods of hygiene now allow cities to sustain themselves, urban fertility rates usually remain substantially lower than rural fertility rates. If global demographic stabilization is the goal, one should champion rather than disparage urbanization. Of course there are other grounds for opposing the further expansion of such megacities as Mumbai, Cairo, or Mexico City, but urban population growth should not blind us to the dramatic downward shift in many developing countries’ overall reproductive rates.