Sadly I fear prison populations follow a trend, and the significant trend (this has been documented), is that there's a higher population of people 'not like us' and which corresponds to the greatest racist perceived notion of threat.
So young black males offer a disproportionately high number of those in prison in the US and the UK, which only proves to white racists that black people have lower moral values, are more inclined to crime, etc., etc. It's a self-fulfilling prophecy because the state in some ways reflects the underlying tensions.
Like when we drive locally, it's always a black driver we see pulled over. When I walk along the busy highroad, the times I smell cannabis wafting from cars. Anecdotal evidence that significant cocaine residue is found in all UK major league football clubs, yet the supporters are by majority white (and remarkably racist). Yet is always black people who get stopped.
Look at the stats taking a white male as the average, then the disproportionately stiffer sentence handed out to women, people of colour, etc.
Factor in the staggeringly high ratio of ex-forces inmates – men who obviously needed, and failed to get, adequate trauma understanding and support.
The study that highlighted the trend in the UK was a long-term study done over generations by an Indian PhD, wish I could find it.
His finding also evidenced that since the emergence of Islamic militancy/terrorism, the percentage Muslim population in prison is also on the rise, suggesting the 'Muslim' is drawing close to the 'Black Man' in terms of the incipient fears of those who sit in judgement upon them.
So for me, prison populations tell more about the justice system than the moral values (or lack thereof) of the residents in such institutions.