On the second point: When investors buy stocks, they’re buying a share of future profits. What that’s worth to them depends on what other options they have for converting money today into income tomorrow. And these days those options are pretty poor, with interest rates on long-term government bonds not only very low by historical standards but zero or negative once you adjust for inflation. So investors are willing to pay a lot for future income, hence high stock prices for any given level of profits.

But why are long-term interest rates so low? As I argued in my last column, the answer is basically weakness in investment spending, despite low short-term interest rates, which suggests that those rates will have to stay low for a long time.

This may seem, however, to present a paradox. If the private sector doesn’t see itself as having a lot of good investment opportunities, how can profits be so high? The answer, I’d suggest, is that these days profits often seem to bear little relationship to investment in new capacity. Instead, profits come from some kind of market power — brand position, the advantages of an established network, or good old-fashioned monopoly. And companies making profits from such power can simultaneously have high stock prices and little reason to spend.

Consider the fact that the three most valuable companies in America are Apple, Google and Microsoft. None of the three spends large sums on bricks and mortar. In fact, all three are sitting on huge reserves of cash. When interest rates go down, they don’t have much incentive to spend more on expanding their businesses; they just keep raking in earnings, and the public becomes willing to pay more for a piece of those earnings.

In other words, while record stock prices do put the lie to claims that the Obama administration has been anti-business, they’re not evidence of a healthy economy. If anything, they’re a sign of an economy with too few opportunities for productive investment and too much monopoly power.

So when you read headlines about stock prices, remember: What’s good for the Dow isn’t necessarily good for America, or vice versa.