Reports indicate that the number of unauthorized immigrants in the US has reached a record high, with some estimates suggesting as many as 14 million. The demographics and characteristics of this population are being studied, including their tax payments and birth rates, with approximately 9% of US births in 2023 attributed to unauthorized or temporary legal immigrant mothers. The exact number of undocumented immigrants who may have left the US recently is uncertain, with some researchers saying it's too soon to determine.