What happened 

Shares of Stamps.com (STMP) fell as much as 19.5% in trading on Thursday after announcing fourth-quarter 2020 financial results. Some of those losses were clawed back late in the day, but shares still lost 15.6% at the close of the market. 

So what

Revenue jumped 28% versus a year ago to $206 million, and net income rose 129% to $46.5 million, or $2.36 per share. On an adjusted basis, earnings were $4.13 per share, up 95% from a year ago. Analysts were only expecting $189 million in revenue and $2.62 per share in earnings on an adjusted basis, so it wasn't Q4 results that disappointed investors. 

Stack of boxes in front of a residential front door.

Image source: Getty Images.

What was concerning is that the jump in revenue and earnings might not last. Management said there was "substantial uncertainty in 2021" as the world recovers from the COVID-19 pandemic. That may result in less e-commerce shopping, which would hurt results.

Now what

Management didn't say that Stamps.com's business would suffer in 2021, just that results may not be predictable given the likely change in consumer behavior as the economy opens up. But it's worth keeping an eye on the company's performance as an indicator of e-commerce activity overall. This could be an indicator that shopping from home may slow down dramatically this year.