Problem: Over the past 30 years, the number of undocumented immigrants in the United States: Over the past 30 years, the number of undocumented immigrants in the United States: has decreased because of poor economic conditions in the United States has decreased because of greater border security has increased due to the lessed population in the United States has increased because of the demand for menial laborers in the United States has grown has increased because of more relaxed border security since September 11, 2001