Yes, the words of the authors. But the final accounting according to the data of the authors: during incarceration they commit no crimes against society and after incarceration they resume committing crime at the same rate as if they had not been locked up. So, longer incarceration reduces crime.
I don't know if that conclusion is actually true or not. It seems as though it would be as long as criminality didn't increase after incarceration to an extent that more than canceled the reduction during incarceration, but they claim that doesn't happen. Well, okay then, longer sentences reduce crime by, as they say, "incapacitating" the criminal during his incarceration.
Killing them would also reduce crime (https://imgs.xkcd.com/comics/cells.png) but I don't think that this is enough of a metric to judge something as good for society
I don't know if that conclusion is actually true or not. It seems as though it would be as long as criminality didn't increase after incarceration to an extent that more than canceled the reduction during incarceration, but they claim that doesn't happen. Well, okay then, longer sentences reduce crime by, as they say, "incapacitating" the criminal during his incarceration.
They seem to be burying that lede.