In the following chart, we see the same visas as above, combined as a group, with their expiration duration extrapolated. The work-years consistently remain at or above 1 million since the year 2000.
In 2008, employment levels for college graduates declined by 106,000. During that same year 1.46 million non-immigrants were hired, thus, incumbent workers lost 1.56 million jobs. In fact from 2007, to 2011, untold numbers of US workers and possibly temporary foreign workers lost million of jobs, due to the incessant importation of temporary worker. Even though employment was growing, the flood of foreign workers made it impossible for separated workers to rejoin the workforce for several years.
This brings us to the data that started me wondering if there is a correlation to the addition of educated workers with worsening employment opportunities. The chart below compares the percent of bachelor degree'd and above (again age 25 and older) with the percentage of bachelor degree'd and above within the entire civilian population. In this data, there is no distinction between citizen workers and immigrants, but we see that around the year 2000, temporary foreign workers began to increase, while the opportunities for college graduates decreased. Note that this is many years prior to the great recession.
Nonimmigrant Visas by Individual Class of Admission (e.g. A1, A2, etc.)*