This article originally appeared on CFO.com.

Where are the mergers and acquisitions?

Consumer confidence is high. Equity values have been climbing for years, and the markets have seen a significant bump since the presidential election, with the Dow Jones Industrial Average climbing 22% and the Nasdaq Composite 24% [as of Sept. 19].

And yet M&A activity appears stalled. Through mid-September this year, just $2.4 trillion in deals have been announced; that’s 23% lower than the value of deals by this point in 2015. Despite a few blockbusters like Amazon’s acquisition of Whole Foods and United Technologies’ bid for Rockwell Collins, this year there have been only 24 megadeals—those totaling more than $10 billion in value—compared with 38 over the same period in 2015.

Even the size of megadeals has shrunk: The average one in 2015 was $24.5 billion. This year, it is $17.6 billion. Markets and mergers have diverged before—in 2015, for example, M&A activity hit an all-time high even as the Dow Jones Industrial Average wandered erratically. But why, in 2017, is deal value moving south while equity values are moving north? Three factors explain the current gap.

The first is the change in tax inversion rules that the Treasury Department put in place in April 2016. In years prior, companies announced numerous deals (many were not consummated) whose principal thesis was not strategic, but rather were aimed at reducing tax obligations by “moving” to lower-tax domiciles. Most of these deals—the scuttled merger of Pfizer and Allergan was perhaps the most prominent—were megadeals, given requirements regarding the size of companies acquired for purposes of an inversion relative to the size of the acquirer.

Read the full article at CFO.com.

Dale Stafford is a partner with Bain & Company and leads its Mergers and Acquisitions and Corporate Finance practice in the Americas.