There's no doubt that the crack epidemic and the drug war more generally is a huge explanation for the growth and incarceration. Young white men and young black men use drugs at about the same rate if anything young whites may use drugs more right but they're much less likely to spend time in prison because of that. So we see these these sentencing the the role of policing and prosecution and sentencing having these real disparate impacts on different socio demographic groups. The other part of you just alluded to is demographics right a huge I've always believed I thought I saw evidence to back it up but of course I was just confirming my bias with this book.
Becky Pettit of the University of Washington and author of Invisible Men talks with EconTalk host Russ Roberts about the growth of the prison population in the United States in recent decades. Pettit describes the magnitude of the increase particularly among demographic groups. She then discusses the implications of this increase for interpreting social statistics. Because the prison population isn't included in the main government surveys used by social scientists, data drawn from those surveys can be misleading as to what is actually happening among demographic groups, particularly the African-American population.