The state of Oregon’s latest prison population forecast is a blast of good news, a clear signal that the state’s efforts to stem the unsustainable growth in our correctional system might be starting to bear fruit.

The latest forecast, released this week, suggests that Oregon’s prison population will drop by more than 500 inmates over the next two years.

That’s a sharp contrast from the forecast of six months ago, which projected continued steady growth in the inmate population — although it did say that the rate of growth was beginning to slow.

Well, that was a snippet of good news — but the prospect of continually steering more money into the Department of Corrections, at the expense of other vital programs such as community-based corrections, wasn’t promising.

All the more reason to cheer the remarkable turnaround chronicled in this week’s forecast.

The biggest factor behind the turnaround: The package of reforms approved by the 2013 Legislature, including a reduction in sentences for certain drug and property crimes. The key bill in the package, House Bill 3194, also lowers penalties for some driving with a suspended license and marijuana-related charges.

It’s worth noting that Albany Rep. Andy Olson, a Republican, was a key player in getting the Legislature to sign off on these changes.

The sheer numbers tell the story: The number of inmates in Oregon prisons now is expected to peak next month at 14,642 — and then drop to 14,132 by January 2016.

Compare that to the projection of just six months ago, which said that Oregon was on track for 16,239 prisoners by the end of the decade. According to a story this week in The Oregonian, corrections officials believed the bill for those extra inmates would have added up to $600 million or so.

Now, the Department of Corrections can put aside plans to put mothballed prisons back on line. Plans to build new prisons (including the state’s 16th prison, in Junction City) can be delayed, at least for the time being.

And the money that we were going to spend on prisons — typically, the most expensive part of the entire correctional system — can go to other purposes, including community-based correctional programs that are more effective and considerably less pricey.

Olson has told the Democrat-Herald’s editorial board that he’s working on some additional proposals for the Legislature to consider in its 2014 session, including one which would give younger offenders a chance to move out of Oregon Youth Authority facilities.

The good news in this week’s prison population forecast should only strengthen the hand of Olson and his colleagues in pushing for another wave of badly needed — and cost-effective — reforms.