WASHINGTON - Here's a somber thought: We may never - or at least not anytime soon - regain "full employment," meaning an unemployment rate between, say, 4 percent and 5.5 percent.
It is now four years from the recovery's start, and the number of jobs is still 2.2 million below the pre-recession peak.
Since World War II, this has never happened. After the harsh 1981-82 recession, employment recouped lost ground in 12 months.
Economists are searching for an explanation, and one recent candidate seems surprising: high-tech.
It's usually seen as an engine of growth, but the spread of automated processes and robots has actually acted as a drag on job creation and has kept the unemployment rate high (7.6 percent in June), argue Erik Brynjolfsson and Andrew McAfee of the Massachusetts Institute of Technology.
Digital technologies, they contend, have enabled companies to cut costs, increase productivity (aka, efficiency), improve profits and slash payrolls. They expect more of the same.
"The MIT academics foresee dismal prospects for many types of jobs as these powerful new technologies are increasingly adopted not only in manufacturing, clerical and retail work but in professions such as law, financial services, education and medicine," writes David Rotman in an informative story in the MIT Technology Review.
A gap has opened between productivity increases and employment growth, goes the theory.
If it persists, it would confound economic history.
Technological upheavals routinely disrupt. Airlines and interstate highways decimated railroad passenger service. Between 1945 and 1970, intercity rail travel dropped nearly 90 percent.
Air conditioning drew people and plants to the South from the Northeast and Midwest.
Early in the 20th century, supermarkets - a more efficient form of organizational technology - displaced small grocers.
"While selling food cheaply was good for consumers, it was bad for the hundreds of thousands of retailers, wholesalers and manufacturers who needed high food prices in order to make a living," writes Marc Levinson in his book "The Great A&P and the Struggle for Small Business in America."
But these and other large technological shifts - from steam power to electrification - typically haven't spawned the permanent rise in unemployment feared by Brynjolfsson and McAfee, says Harvard economist Lawrence Katz.
Some existing workers lost their jobs; it was hard on them. Yet, there were always "new sources of labor demand" that have prevented a steep run-up in unemployment.
This is the crux of the matter. Productivity-enhancing technologies usually create more demand than they destroy, through two channels.
First, lower prices enable consumers to buy more.