Maybe more jailing, less crime?

I was amused to hear the talking heads on the radio  today say, in connection with President Obama's visit to a prison, that we should stop the incarceration emphasis of the last three decades because crime rates have fallen so low. Might they not think that many logical listeners would think that there just might be a link between a higher jail rate and a lower crime rate? Or  does the lower crime rate mostly stem from the aging of the population?

-- Robert Whitcomb