What happened

Shares of The Trade Desk (NASDAQ:TTD) fell 18.5% in December, according to data from S&P Global Market Intelligence, in the wake of the the broader markets pulling back and the programmatic advertising specialist announcing the resignation of its chief operating officer.

On the former, the S&P 500 dropped a whopping 9% last month on worries of political tensions and slowing global economic growth. Considering The Trade Desk stock still managed to soar more than 150% for all of 2018 -- with big moves driven largely by several significantly better-than-expected quarterly reports over the past year -- it wasn't terribly surprising to see it pull back a little more than most as the broader markets retreated.

Falling stock chart superimposed over columns of blue numbers

Image source: Getty Images.

So what

Still, it's worth noting Trade Desk did fall modestly (around 2%) on the heels of its Dec. 4 announcement that COO Rob Perdue will step down from his post following a "transition period" in the first half of this year. But investors should take solace knowing that announcement was largely positive in tone.

"Since joining The Trade Desk in 2013, Rob has build an amazing operational team and has been instrumental in helping to build the special culture we have here," stated founder and CEO Jeff Green. "I'm grateful to Rob for everything he's done for The Trade Desk, and for his leadership and friendship over the years."

"After a conversation with Jeff, we agreed that with The Trade Desk's strong operational foundation and solid growth plans for the future, this is the right time for me to move on to the next phase of my life," Perdue elaborated. "Personally, I look forward to my next chapter and to spend more time with my family."

Now what

The company says it's begun a search for Perdue's replacement "to ensure a seamless transition as The Trade Desk continues to deliver strong momentum and global growth." 

So unless we receive any further updates in the coming weeks, investors will need to wait until The Trade Desk releases fourth-quarter 2018 results in late February for more details on its recent momentum.

Steve Symington has no position in any of the stocks mentioned. The Motley Fool owns shares of and recommends The Trade Desk. The Motley Fool has a disclosure policy.