According to an analysis by the Tax Foundation, an independent think tank, six states — California, New York, New Jersey, Illinois, Texas and Pennsylvania — claim more than half of the so-called SALT deduction. The vast majority of those taxpayers are clustered around wealthy cities on the coasts, as shown in the county-by-county breakdown on this interactive map.

The other, more controversial idea is to reduce the cap on the mortgage interest deduction, which subsidizes homeownership by allowing people to deduct the interest on their mortgage debt. The bill as written would reduce the cap to $500,000 in debt from $1 million today. The change would only apply to new mortgages, so people already getting the benefit would be grandfathered in.

This will not affect most places. The median home price in the United States is about $200,000, and less than 3 percent of homeowners have more than $500,000 in debt, according to data from CoreLogic.

But California is not most places. Because it has the priciest real estate markets in the country, state taxpayers get a huge benefit from writing off their mortgage debt. According to Zillow, there are only four metropolitan areas in the United States where more than half of homes are priced above $500,000: San Jose, San Francisco, Los Angeles/Orange County and San Diego.