The population of undocumented immigrants in the US fell from 12 million to approximately 11 million during the height of the financial crisis (2008-09) . . . And since then, Mexicans without documents aren’t migrating at rates to replace the loss, creating a net zero balance for the first time in 50 years.
Of course, while the number of undocumented immigrants overall has held steady, the population of the United States as a whole relentlessly, but slowly, grows. So, the percentage of the United States population that does not have lawful immigration status continues to fall, and is currently a bit more than 3.3% of the total population of the United States.