Final answer:
Mexican immigration has changed from back-and-forth migration to more permanent, one-way migrations, influenced by stricter immigration policies such as the Immigration Reform and Control Act of 1986. The demographic and economic nature of immigration has also shifted, with a larger proportion of immigrants coming from Mexico and other parts of the Americas, serving crucial economic roles.
Step-by-step explanation:
One way that Mexican immigration to the U.S. has changed over the years is the shift from circular or back-and-forth migration patterns to more permanent, one-way migrations. Sociologist Douglas Massey suggests that despite the average standard of living in the U.S. being lower than some expect for immigrants, the steep enforcement of immigration laws, particularly after the Immigration Reform and Control Act of 1986, has made it more difficult for Mexicans to return home, resulting in a predominance of illegal one-way immigration. This change in immigration pattern has been partially attributed to the unintended consequences of stricter immigration policies.
Additionally, the nature of immigration has changed economically and demographically. Historically, the U.S. had primarily European immigrants, but by the 2000s, around half of U.S. immigration came from the Americas, especially Mexico. The immigrants have served important roles in the economy, often taking on jobs that domestic workers are less willing to do, and have been instrumental in sectors like agriculture, domestic work, and caregiving.