Mass incarceration in the United States disproportionately impacts African American and Latino communities. Michelle Alexander, author of The New Jim Crow: Mass Incarceration in the Age of Colorblindness (2010), argues that mass incarceration is best understood as not only a system of overcrowded prisons. Mass incarceration is also, "the larger web of laws, rules, policies, and customs that control those labeled criminals both in and out of prison." She defines it further as "a system that locks people not only behind actual bars in actual prisons, but also behind virtual bars and virtual walls", illustrating the second-class citizenship that is imposed on a disproportionate number of people of color, specifically African-Americans. She compares mass incarceration to Jim Crow laws, stating that both work as racial caste systems.