On the campaign trail in 2008, Barack Obama promised to create 5 million green jobs across the nation. Depending on how you define green jobs, he either did incredibly badly on this front — helping to create less  than 3,000 jobs — or quite badly — adding about 700,000 jobs after the passage of the 2009 stimulus.

But there’s a gigantic problem with the latter estimate: It counts all mass-transit and construction jobs as being green because the industries follow green principles. So bus drivers and ditch diggers are green employees.

As you probably suspected, the group that put out the report had a motive to put its thumb on the scale. It’s from the Environmental and Energy Study Institute,  “a 501(c)(3) non-profit organization dedicated to promoting environmentally sustainable societies.”

On the campaign trail in 2010, Jerry Brown promised to create 500,000 green jobs in California. A year later, The New York Times scoffed at his vow.

In the Bay Area as in much of the country, the green economy is not proving to be the job-creation engine that many politicians envisioned. … Gov. Jerry Brown promised 500,000 clean-technology jobs statewide by the end of the decade. But the results so far suggest such numbers are a pipe dream….

The Economic Development Department in California reports that $59 million in state, federal and private money dedicated to green jobs training and apprenticeship has led to only 719 job placements — the equivalent of an $82,000 subsidy for each one.

In early 2013, California greens celebrated a report that said the Golden State led the nation in creation of green jobs in 2012 with 26,000. But that figure once again included categories of jobs like mass transit and construction — no surprise since the report didn’t come from a respected think tank but from Environmental Entrepreneurs, a de facto lobbying front for government-subsidized green projects.

And what do the think tanks say? The Brookings Institution, considered liberal to moderate, echoed McKinsey’s findings in its 2011 report, estimating that green jobs constitute about 2 percent of the total economy — and that too was with a definition that included many construction jobs. A twist to the Brookings report: It found there were fewer green jobs in Silicon Valley in 2010 than 2003.

So when the new leader of the California Senate talks up green jobs, he’s going down a well-trod path. If his promises come true, that will be a first.

As The New York Times noted in 2011, it’s just wrong to depict green jobs as emerging as a central pillar of the U.S. economy.

But it is a talking point that remains beloved among greens, if not among economists.