Those days are over, at least for the moment. In normal times, markets are driven much less by what governments do and much more by, well, the economic fundamentals. How many people are working, with what level of productivity and savings levels, and what are the resulting economic growth rates, levels of corporate profitability, and interest rates?

Even though it is a historical aberration, doesn’t the very low stock market volatility of 2017 make more sense than the kind of wild swings we saw until recently? Why should the collective value of major companies swing by more than 1 percent three days out of 10?

After all, the assets of those major companies — Exxon Mobil’s oil rigs and Google’s search algorithm and all the rest — don’t really change from day to day. All that changes is investor perception about what kind of cash those assets will generate in the future. Isn’t it actually fairly rare that a piece of news should change the fundamental outlook by that much?

What makes this moment unusual is that there really are policy choices in play that could have hugely distortive effects on those fundamentals: what happens to trade policy, taxes and health care in the United States; what terms Britain achieves in its exit from the European Union; even whether the E.U. as we know it survives.

But if the last few years have taught investors anything, it is that those with a hair-trigger reaction to political news stand to lose, while those who bet on a continued steady and unexceptional expansion will win.

You see a bit of that in how subsequent conflicts over United States fiscal policy during the Obama years generated less market volatility. The debt ceiling standoff of 2011 generated huge market swings as traders bet on the risk of a default; the standoffs over the “fiscal cliff” at the end of 2012 and a government shutdown in October 2013 caused mere murmurs.