A study last year by the Organization for Economic Cooperation and Development found that, for most major economies, rising productivity was a more important driver of gross domestic product growth between 2000 and 2017 on average than population growth or change in the employment rate. More than 90% of China’s potential growth in 2017 came from productivity increases, the most of any country and a few rungs ahead of the U.S. For Saudi Arabia, however, 62% came from population growth alone—and Nigeria is even more reliant than the Arab kingdom on the sheer size of its potential labor and consumer pool. France stands out for balancing increased productivity and population with higher employment, likely boosted by a healthy influx of working-age immigrants and its generous labor benefits.
Population is just one of three factors influencing national economies.
Productivity gains can make up some of the gaps as populations taper off and begin to shrink, but it's a much more challenging way to grow an economy and may not be sustainable over time: For most of the countries in the OECD’s study, the relative contribution of productivity to growth has fallen over time.
Ultimately, no country will be left untouched by demographic decline. Governments will have to think creatively about ways to manage population, whether through state-sponsored benefits or family-planning edicts or discrimination protections, or else find their own path to sustainable economic growth with ever fewer native-born workers, consumers, and entrepreneurs.
https://www.bloomberg.com/graphics/2019-global-fertility-crash/?srnd=businessweek-v2