Two years ago I wrote: Demographics and GDP: 2% is the new 4%. As I noted, "One simple way to look at the change in GDP is as the change in the labor force, times the change in productivity. If the labor force is growing quickly, GDP will be higher with the same gains in productivity. And the opposite is true."



Obviously demographics are important for GDP.



Last week, Goldman Sachs economist Daan Struyven wrote: Immigration Restrictions: A Downside Risk to the Economy's Speed Limit. Here are few excerpts from his note:



The contribution from net immigration to total population growth has risen from 30% in the 1990s to 40-50% recently as the natural increase in population has slowed. The effect of immigration on growth of the labor force is even more pronounced as immigrants tend to be younger and therefore more likely to participate in the labor force than the native-born population. As a result, net immigration currently accounts for virtually all of the 0.5% trend increase in the labor force.



Reduced immigration would result in slower labor force growth and therefore slower growth in potential GDP—the economy’s “speed limit”. In addition, academic studies suggest there could be negative knock-on effects on productivity growth. As a result, we see immigration restrictions as an important source of downside risk to our 1.75% estimate of potential growth.

The claimed returns to Trumpnomics are close to the highest growth rates we’ve seen under any modern administration. Real GDP grew 3.4 percent annually under Reagan; it grew 3.7 percent annually under Clinton ... But there are fundamental reasons to believe that such growth is unlikely to happen now.



First, demography: Reagan took office with baby boomers — and women — still entering the work force; these days baby boomers are leaving. ... Just on demography alone, then, you’d expect growth to be around a percentage point lower than it was under Reagan.

As Struyven notes, immigrations restrictions will lower potenetial GDP.And yesterday, Professor Krugman wrote: Trump’s Rosy Scenario CR Note: It seems very unlikely that growth will pick up sharply, especially if there are severe immigration restrictions.