That's what I thought at first, but read it again.
"We predict that we will not be able to sustain the growth in migration," because of a drop in birth rates here, she said.Perhaps she is just mourning the potential loss of revenue for Mexico. After all, the fewer migrants there are up here, the less money (remittances) there is being sent back to Mexico.
(What do you think?)
Decreasing birth rate is the reason for fewer 'bodies' available for cheap labor in the US. Therefore a loss of revenue to Mexico as you say. It's a loss all the way around. Lost revenue to Mexico from less funds sent back and loss of profits by US businesses due to loss of cheap labor.
How in the world could they expect to sustain a positive birth rate in Mexico when more and more of their population, of child bearing age, reside in the USA?