In the 1960s Mexican mothers had nearly seven children each (whereas women in India then had fewer than six). The average now is just over two—almost the same as in the United States. The UN reckons that from 2040 the birth rate in Mexico will be the lower of the two.
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History teaches caution in assessing the link between demography and migration. The Mexican baby boom of the 1950s coincided with lowish emigration, whereas the exodus to the United States kicked off in the 1980s, just as Mexico’s birth rate was plummeting. Today’s falling fertility rate will curb the flow. But the main motors of migration will still be economic boom or bust—on both sides of the border.