It’s as if the stock market adopted Bobby McFerrin’s “Don’t Worry, Be Happy” as its mantra on the way to record highs this past week. It certainly had the potential to be an ugly week. The number of Americans hospitalized because of Covid-19 crossed 90,000 for the first time, and Thanksgiving celebrations were far more muted than usual. Jobless claims jumped for a second week in a row, signifying further weakness in the labor market. Even questions about the results of AstraZeneca’s (ticker: AZN) Covid-19 vaccine trial, which...