Also, the new arrival data are almost certainly understated. Nonetheless, this oversimplified analysis gives us some insight into out-migration. If we compare these results to the 2006 to 2009 period we see a very different pattern. Table 3 shows that the likely illegal population actually fell from 7.282 million in 2006 to 6.703 million in 2009 -- a 579,000 decline. The arrival data from 2009 show 665,000 new arrivals from 2006 to 2009. For the number to fall 579,000, even with 665,000 new arrivals, out-migration would have to equal 579,000 plus 665,000 for a total out-migration of 1.244 million. Thus, out-migration in the 2006 to 2009 period would seem to be more than twice as large as in the 2002 to 2005 period. Also 665,000 is about 32 percent less than 981,000, implying a one-third decline in the number of new arrivals. While this analysis is oversimplified and does not include other things that can reduce the likely illegal population, as we will see these other factors do not change that much over time. As a result, even this simplified analysis based on grouped-year-of-arrival data shows that out-migration must have increased significantly for the numbers to look as they do. The only alternative interpretation is that somehow the share of people in our target population who die, age out, or get more education suddenly changed. This would mean the decline was not the result of an increase in return migration. But we find no evidence that this is the case.