Can someone explain to me a model of an economy where this makes sense?

For the economy, a slower increase in the population raises concerns about American competitiveness. But it could actually be a good thing. A number of economists, including the Federal Reserve Chairman Ben Bernanke are worried about the lack of inflation and income growth in the United States. Fewer workers could drive up salaries. What’s more, fewer new Americans might help slow government spending. That may curtail the rising US federal debt, which many think will soon cause interest rates to jump and hold down US GDP growth. “At a time of fewer government resources, fewer new people might not be such a bad thing,” says New Hampshire’s Johnson.

This seems very wrong to me. For one thing we have an aging population who we are going to need to support, and the less working age population we have to support them the more of a burden they become. Like a pyramid scheme you can’t permanently improve this situation with faster and faster population growth, but you certainly can make the situation worse by decreasing the number of working people per retired person. In addition, lots of government spending, like defense spending, is non-rivalrous public goods so that a higher the population means a lower the per-capita cost. I’m very curious to hear how Kenneth Johnson, the “population expert” from which this claim comes, sees per-capita government spending decreasing. Or perhaps he is talking only about total spending, but why should that be a concern?

Likewise I find his claim that lower population growth will drive up salaries to be confusing. After all one man’s salary is another man’s price, which decreases his real wage. Perhaps he thinks there are basically two types of people: skilled and unskilled. And that what’s really happening is population growth is decreasing in the unskilled which will make them more scarce relative to the skilled, and thus able to command a higher wage. I don’t find this very believable, either empirically or as a model for our economy.

Can someone explain to me a model where decreasing population growth raises real wages and decreases per capita government spending? I do not mean to be dismissive of Professor Johnson or his claims, but I am at a loss here.