Can U.S. economic growth continue forever? The economist Robert J. Gordon doubts that the country is innovating at a rate that will match the last 250 years.

Even if Americans continue innovating at the same rate of the two decades prior to 2007, the country will still face six specific challenges that will drag down growth, he wrote in a paper: demographics, education, inequality, globalization, energy and environment, and consumer and government debt, he argues.

In a 2013 TedTalk called “The death of innovation, the end of growth,” Gordon gives the audience an experiment:

“You have to choose either option A or option B. Option A is you get to keep everything invented up till 10 years ago. So you get Google, you get Amazon,you get Wikipedia, and you get running water and indoor toilets. Or you get everything invented to yesterday, including Facebook and your iPhone, but you have to give up, go out to the outhouse, and carry in the water. Hurricane Sandy caused a lot of people to lose the 20th century, maybe for a couple of days, in some cases for more than a week, electricity, running water, heating, gasoline for their cars, and a charge for their iPhones. …

“I’d like to award an Oscar to the inventors of the 20th century, the people from Alexander Graham Bell to Thomas Edison to the Wright Brothers, I’d like to call them all up here, and they’re going to call back to you. Your challenge is, can you match what we achieved?”

Watch the TedTalk here: