California is home to four of the world's "impossibly unaffordable" housing markets, according to a recent study. The annual Demographia International Housing Affordability report, produced by Chapman University and the Frontier Center for Public Policy, warns that high housing prices in relation to incomes are hindering upward mobility and causing social stratification in the Golden State. Urban containment policies aimed at limiting sprawl and increasing density have led to skyrocketing land prices, resulting in unattainable home prices. The report highlights the impact on young people, minorities, immigrants, and the middle class, noting that restrictive housing policies have regressive effects. It calls for cities to open up land availability to reduce housing costs and combat the housing crisis that threatens the middle class. With the disappearance of affordable starter homes, millennials are struggling to upgrade to larger homes, leading to unsold properties and lower asking prices in the U.S. housing market.