All 50 states have laws that require people to be U.S. citizens in order to register to vote in federal elections, but none of them require proof of U.S. citizenship in order to do so. Several states tried to enact such a requirement, but they were blocked by court rulings. Some states require voters to submit Social Security numbers and perform checks on them, but the chief actuary of the SS Administration estimated in 2013 that about 0.7 million illegal immigrants worked in 2010 by using SS numbers obtained with "fraudulent birth certificates" and 1.8 million worked by using SS numbers "that did not match their name." Likewise, California Democrat Kevin De Leon stated in 2017 that "anyone who has family members who are undocumented knows that almost entirely everybody has secured some sort of false identification," such as "a false Social Security card." In 2016, Barack Obama stated that voting records are not cross-checked against immigration databases.