LIKE the weather in Chicago, you don’t have to wait long for a new trend in the stockmarkets. Just a few weeks ago, investors seemed to have second thoughts about their Trump-related euphoria (which itself was a contrast to the widespread nervousness ahead of the election). Now they have been recording new highs again.

While the spark for the rally seems to have been a presidential comment about forthcoming tax cuts, the causes have been much broader; the MSCI World Index has also hit new highs. Commodity prices have perked up, which may be a sign that the Chinese economy is holding up (if you recall, a Chinese slowdown was the big worry 12 months ago). Asian trade has perked up after a long period of sluggishness (the exports of South Korea, a bellwether in this respect, have risen for three months in a row). According to SocGen the global purchasing managers index for manufacturing was close to 50 (unchanged output) at the start of 2016; now it is above 53. The IMF is predicting global growth of 3.4% this year, up from 3.1% in 2016. Inflation has surprised on the upside—a consequence of commodity price rises, perhaps, but a relief for those worrying about deflation.

Analysts look confident about their expectations for profits growth this year; at the global level, they are forecasting 12.6%, according to Bank of America Merrill Lynch. But they made similar predictions for 2015 and 2016, when profits fell 0.7% and rose 2.4% respectively. American companies do seem particularly confident; more than 50% of earnings calls used the world “optimistic” according to BAML, the highest since 2003. Corporate tax cuts will, of course, boost earnings per share, and there are hopes of deregulation too.

All this may sit rather oddly with the general air of political turmoil that has set in since June and the Brexit vote. Of course, while Mr Trump’s bizarre news conferences and tweets entertain and appal the media, some developments are just “noise”—why should a pension fund care about the status of the national security adviser or labour secretary? But the election of Marine Le Pen as French president would be a real threat, given her proposal to redenominate French debt into francs, and investors seem to be taking it more seriously as the FT reports today.

The risks are high that investors might be disappointed. It is not clear that America’s fiscal stimulus will be as large as investors hope (especially on the infrastructure side) given Congressional doubts. The Fed seems set to tighten policy—a sign that the American economy has recovered, yes, but a big test for a market that has been coddled by near-zero rates since 2009. The talk of trade wars has not gone away, as Willem Buiter of Citigroup writes:

The risk of a significant increase in protectionism, up to and including “trade wars”, is material and rising, and that its potential consequences on growth and financial markets could be large.

And valuations remain high, by historical standards. The cyclically-adjusted price-earnings ratio of the American market (which averages profits over 10 years) is 28.7, compared with a historic average of 16.7. That is not a great short-term market indicator but still it emphasised that optimism about profits is high at a time when profits have only just come off a post-war peak as a proportion of GDP. So this latest trend may be as short-lived as the previous ones; President Trump should be careful about claiming credit for the stockmarket. You never know what will happen next.