What kind of evidence does Michelle Alexander gather to support her claims in The New Jim Crow?

Michelle Alexander uses primarily objective evidence in The New Jim Crow. The majority of her evidence is drawn from the legal system and the judicial system. She includes academic studies, as well, which rely on analyzing primary data on demographic and sociological factors.
Alexander includes historical information on the US judicial apparatus, including state and federal aspects, to show the discriminatory practices that upheld unequal treatment of African Americans. Among the things she considers are landmark Supreme Court cases that supported discrimination. For example, Plessy v. Ferguson supported "separate but equal" ideology.
Also, changes in laws are discussed in relation to their effects. While Brown v. Board of Education overturned school segregation, states and school districts often complied slowly or made legal objections so that schools remained entirely segregated or nearly so.
In addition, Alexander looks at statistics about poverty, arrests, and incarceration, especially for Black Americans, to show the extent of change or continuity in the wake of legal/judicial changes.