Stocks have entered the new year with their wonted ability to waft effortlessly higher on thermals of giddiness and so-so volume evidently still intact. In decades past there have been instances where the mere flipping of the calendar to January was enough to evince a sea change in Wall Street’s mood. Not this year, apparently — at least not so far. The headlines have been so felicitous lately — even Trump has been getting good press — that it’s almost scary.  One could imagine that all that’s needed to send stocks tumbling is for some high-profile economist to say — and really mean it — something to the effect that the stock market seems to have reached a permanently high plateau.