Book excerpt: The study, which looks at California's housing crisis and its root causes, cautions that the current situation has serious implications for the families affected, the communities in which they live, and the well-being of the state's economy. [...] In order to meet the basic shelter needs of low-income Californians, the state needs an additional 651,000 affordable rental units." The new report finds that: • In 2001, one-quarter of the renter households in the state's metropolitan areas - 1 million out of 4.1 million - spent more than half of their incomes on rent. [...] The report identifies the following causes of the state's housing crisis: • Inadequate production of new housing units: According to the state Department of Housing and Community Development, California needs to build more than 200,000 housing units per year, through 2020, in order to keep up with population growth and maintain "reasonably affordable" housing. [...] "Additional state and federal support is needed to address the needs of those who are not being served in the current housing market, including the homeless, seniors, and low-income renters." The California Budget Project (CBP) was founded in 1994 to provide Californians with a source of timely, objective, and accessible expertise on state fiscal and economic policy issues. [...] The CBP engages in independent fiscal and policy analysis and public education with the goal of improving public policies affecting the economic and social well-being of low- and middle-income Californians.