California, with approximately 12% of the nation's population, has around 30% of the nation's welfare caseload in terms of individuals and families. Here's a telling chart from the website of Chuck Devore, a candidate for the U.S. Senate from California.
State welfare officials estimate that cutting off payments to illegal immigrants for their U.S.-born children could save about $640 million annually if it survives legal challenges.
California has roughly 2.7 million illegal residents, according to an April 2009 report from the authoritative Pew Hispanic Center, accounting for about 7% of the state's population. State officials estimate that they add between $4 billion and $6 billion in costs, primarily for prisons and jails, schools and emergency rooms. Beyond those services, the illegal population adds to the overall cost of other parts of local government, from police and fire protection to highway maintenance and libraries.
California's current budget deficit is around $20 billion.