The U.S. Citizenship and Immigration Services (USCIS) has published a fact sheet with information on the population of Lawful Permanent Residents, Age 50 and Over applicants that are eligible for naturalization. This fact sheet provides information on Lawful Permanent Residents, Age 50 and Over with Lawful Permanent Residence (LPR) status, also known as Green Card holders. I have included the link to the USCIS fact sheet below.
Source of Information:
USCIS (USCIS.gov), USCIS Newsroom: Fact Sheets