What happened
Shares of Appian Corp (APPN 10.94%) were falling today as investors processed information about new jobless claims and a spike in coronavirus cases in a handful of states. As of 2:58 p.m. EDT, Appian's stock was down 11.5%.
Now what
Investors across nearly every industry pushed shares down today, as worry set in that a new wave of coronavirus infections was hitting South Carolina, Florida, Arkansas, Nevada, and Oregon. The S&P 500 was down 5.3% by the middle of the afternoon.
With cases of COVID-19 trending up, investors were worried that the second wave of infections could slow down the economy even further, just as some states were opening back up. Those concerns were multiplied by today's jobless claims numbers, in which 1.5 million U.S. workers filed for unemployment over the past week. While the claims were lower than the previous week, the unemployment rate remains at an exceptionally high 13.3%

Image source: Getty Images.
The uncertainty surrounding the economy and how long COVID-19 will continue to affect it likely caused Appian investors to follow the larger market trend today and sell off some of their shares.
So what
In general, investors had been very optimistic over the past few months. So it's not entirely surprising that a pullback in the market occurred today.
With so much uncertainty around how businesses will fare after being shut down for months and how long the unemployment rate will remain in the double digits, some investors may finally be realizing that the U.S. economy may take longer to bounce back from the effect of the virus than they had previously thought.