One of the many fallacies of the 2016 election is a belief that politicians can significantly increase the growth rate of the U.S. economy. 

To be sure, the current slowdown is one of the most difficult economic challenges we have faced since the end of World War II, but there is very little the next president can do to change it. 

Real economic growth rates are driven by much broader forces than tax rates, regulation and trade policy. 

There is ample evidence that the current slowdown is the result of significant reductions in labor productivity gains, but that’s something that few politicians understand or mention. 

Last summer, the Wall Street Journal said: “The longest slide in worker productivity since the late 1970s is haunting the U.S. economy’s long-term prospects.” 

The article went on to explain that the productivity conundrum was responsible for the Fed’s decisions to hold down interest rates. It’s also why wages are not growing and why many families feel economically trapped. 

Charts show that labor productivity gains recently dropped to 0.5 percent after growing at annual rates of a little less than 2 percent for much of the time since the mid-1980s. 

There was a period during the early and mid-2000s when technological advances in workplaces pushed productivity gains above 3 percent for five years or so. But then the gains fell back to the more normal (sub-2 percent) range, where they remained until the recent nosedive. 

Productivity gains can, and probably will, move back to the more normal range of 1.5 percent to 2 percent. But there is little reason to think they will climb to the levels politicians want 3 percent, 4 percent or even 5 percent a year.

Marc Levinson, a former economics editor of The Economist, explained why in a recent essay adapted from his book, “An Extraordinary Time: The End of the Postwar Boom and the Return of the Ordinary Economy,” due for release Nov. 8. 

“Historically, booms are the exception and not the norm,” Levinson wrote in The Wall Street Journal. The norm for growth in industrialized economies is 1.5 percent to 2 percent, he said.

The U.S. economy raised expectations by performing extraordinarily well during the decades following World War II when we faced little global competition. 

Such growth was not sustainable, and things began changing in the 1970s. People blamed the oil crisis, but the culprit wasn’t higher gasoline prices. It was that productivity gains had run their course, according to Levinson.

The real drivers of postwar growth, he said were the tens of millions of workers who moved from farms to better-paying city jobs, the nationwide push for high school and college degrees, and efforts in the 1950s and ’60s to create a nationwide interstate highway system to move goods and people. 

More recently, the technology revolution spurred increased productivity, but only for a relatively brief period.

“Productivity growth is something over which governments have little control,” Levinson wrote. 

In the long run, he said, we are better off understanding how growth really occurs and being happy with the progress we are making, rather than continuing to have unrealistic expectations and being repeatedly disappointed.