The fertility rate of Mexico, once among the highest in the world, was approximately at replacement level in 2010, down from almost seven in 1960. This is due to government birth control policies dating back to the 1970s that made heavy use of sterilization in a country with stringent abortion restrictions except in the capital. By the 2000s, about 40% of married Mexican women were sterilized. Women's increased participation in the workforce and improved educational opportunities also played a role in this development. Although the number of new Mexicans each year in the 2000s was the same as those from the 1970s, the rate of growth has slowed substantially. Mexicans' average age was 28 in 2010, up from 17 in 1980. For comparison, Europe took a century rather than 30 years to make the same demographic transition. Mexicans living in the United States had a higher fertility rate than their counterparts in the old country, however, and this means that the number of people of Mexican heritage would continue to grow North of the border. In fact, in the early 2000s, there was significant Mexican migration, legal and otherwise, into the United States, where standards of living and wages are higher.