Federal law requires immigrants to "demonstrate an understanding of the English language, including an ability to read, write, and speak words in ordinary usage" to become a U.S. citizen. However, the law has exceptions for people with disabilities and those who are over certain ages and have lawfully resided in the U.S. for certain lengths of time. Recent immigrants have made less progress in learning to speak English than earlier generations of immigrants. Because communication is essential to productivity, a failure to learn English limits earning power and makes people more reliant on welfare.