Since Republican leaders pushed through their once-in-a-generation tax overhaul, more than 70 major U.S. companies—including Wal-Mart Stores Inc., Apple Inc., and JPMorgan Chase & Co.—have announced either pay raises or bonuses for rank-and-file employees or more hiring and investment.

That's not all that many; there are over 3,500 publicly traded corporations in the U.S., after all. And to some, they amount to little more than well-timed PR stunts designed to curry favor with the public and the president. But they've been enough to get some analysts rethinking just how much the $1.5 trillion package of cuts might benefit ordinary Americans and the broader economy.