Democrats immediately seized on the “longer hours” line, which they called “out of touch.” Bush scrambled to clarify that he was talking about the need for more full-time jobs.

But rather than focusing just on one controversial phrase, it’s worth looking at Bush’s whole statement. Bush is highlighting one of the most basic formulas in macroeconomics: In its most simplified form, a country’s economic output is the product of its number of workers times how many hours they work times how much they can produce in an hour. If you want the economy to grow faster, you have to get at least one of those three factors – workers, hours or productivity — to accelerate.

Right now, as Bush says, the U.S. is struggling in all three areas. Start with the number of workers: Labor force participation — the share of the adult population that’s working or actively looking for work — has been falling for 15 years and is at its lowest level since 1977.