M&A activity slowed significantly in the third quarter. Through Sept. 24, there were 214 U.S. deals of $100 million or more worth a total of $229 billion, according to data from Dealogic. (All deal figures are for transactions worth $100 million or more.) That’s a significant drop from the 263 deals worth a total of $576 billion in the second quarter and the least activity since the first quarter of 2017.

Private equity saw a concomitant decline, with 35 deals of $100 million or more in Q3 worth a total of $39 billion versus 44 deals work $78 billion in Q2. That’s the lowest quarterly deal volume since at least 2014 and the lowest dollar volume since Q1 of 2016. September has been particularly anemic, with 48 U.S. M&A deals worth a total of $34 billion and only three PE deals worth a total of $1.4 billion, though many private equity transactions don’t have announced values and thus aren’t included in Dealogic’s figures.

Absent the September numbers, Q3 has seen healthy activity levels, and some lawyers say the start of the fall is a mere blip and that pipelines remain full. Possible reasons for a slowdown are easy to reel off if hard to prove, from the uncertainty surrounding Brexit to the trade tensions between the U.S. and China, political chaos in the U.S. and signs of a cooling global economy.

In the largest deal announced in Q3, Blackstone Group Inc., CPPIB, GIC Pte. Ltd. and Thomson Reuters Corp. agreed to sell Refinitiv to the London Stock Exchange Group plc for $27.8 billion. Announced Aug. 1, the deal’s whose fate is uncertain given Hong Kong Exchanges & Clearing Ltd.’s hostile offer for LSEG. In quarter’s second largest transaction, CBS Corp. (CBS) and Viacom Inc. (VIAB) announced their long-awaited merger on Aug. 13 in a quiet conclusion to last year’s pitched battle between the CBS board and controlling shareholder Shari Redstone.