You know the mantra. As the beginning of January goes, so goes the month, and so goes the year. And it’s not that off the wall. The first five trading days have gone the same direction as the year 72% of the time over the last 60 years.

This year marked the ninth-most intense upside start for the S&P 500 in the more than half a century, and it’s happened despite some eyebrow-raising economic data and a tall economic order for the year ahead.

As traders embark on a shortened week, key housing and inflation data could offer more enthusiasm. The December readings on housing starts and building permits scheduled to be released Wednesday are expected to show improvement. And the December reading of the Producer Price Index is projected to show that inflation...