Mayor Ed Lee, a big promoter of the Twitter tax break, won't support a tax break aimed at encouraging businesses to hire ex-offenders.

I'm not a big fan of any tax breaks -- mostly because I don't think they work. The typical payroll tax break saves a company a few hundred dollars a year -- nowhere near enough to make an actual difference in a hiring decision.

The Mirkarimi tax break for hiring ex-offenders is much richer -- up to $10,000 per hire. That's real money for some companies -- although, again, I don't know how many actual ex-offenders will get jobs because of it.

Still: The city's facing a serious problem. More than 65 percent of the people now in county jail will eventually be arrested again. The recidivism number goes as high as 75 percent for state prison inmates. And under the governor's realignment plan, San Francisco will be getting around 650 new state prison shifted into our local jail and probation system every year.

And I don't hear many people at City Hall talking about it.

Lee told the Examiner that the Mirkarimi tax break is "not comprehensive enough." Huh? The Twitter tax break was broad, in some cases arbitrary. Now a plan that is aimed not at a high-tech company but at people who have been released from jail and will have serious problems finding employment is "not comprehensive enough."

Look: San Francisco has an interest -- a direct public-safety and economic interest -- in finding work for ex-offenders: If they don't get employed, they're almost certain to go back to crime. Employment is no guarantee that a former inmate will break out of the criminal cycle -- but unemployment is a pretty good guarantee that he or she won't.

So let's be consistent here. If tax breaks work to create or preserve employment, it's cheaper to follow the Mirkarimi plan and give incentives to employers for hiring ex-offenders than it is to re-arrest, re-try and re-incarcerate them. If the Twitter deal made sense, then this one clearly does, too.

Again: I'm not pushing this or any tax break for employers. But what's Lee's alternative? I asked his press spokesperson, Christine Falvey, to share with me the mayor's plan for handing the influx of new inmates (all of whom will be released within a year or two of arrival in the SF county jail), but she hasn't gotten back to me.

We all know what's really going on here -- nobody wants to do anything that looks like it's aimed at helping criminals. I get it. But it's just stupid, since criminals without jobs tend to stay criminals -- and that's not good for anyone in San Francisco.

UPDATE: Falvey emailed me back. She didn't lay out any plan, but did say this:

"The mayor has not stated the he opposes the legislation but in its current form, it seems too narrow. He would like to see some of the categories broadened to include other populations that need support in job placement and retention. The legislation has not been voted on yet and he looks forward to reviewing the final version."