If you’ve been watching the financial news lately, you’ll know that Facebook’s IPO was a dud. And its sinking value on the stock market is apparently pulling other tech companies down into the vortex with it – and Twitter is no exception.

Twitter is not traded publicly, but share are constantly being traded on the secondary market. And since the Facebook IPO, Twitter’s value has dropped by over 15 percent.

Prior to Facebook’s less-than-stellar entry onto the markets, Twitter was being traded at $21 a share on the secondary markets. Now, it’s dropped to $18, the New York Post reports.

This means Twitter’s valuation dropped from $10 billion to about $8.7 billion. Twitter was valued at about $8 billion back in October 2011, but had since increased in value as buzz surrounding the network grew.

As Wire Inc. reports, SecondMarket, the secondary marketplace where Twitter is traded, would not confirm or deny the company’s falling valuation.

Twitter’s stock price might be dropping, but its business is booming. CEO Dick Costolo went on the record this week saying that there are now over 400 million tweets sent every day, which is up 18 percent in just a month. And, Twitter’s mobile ad business surpassed its non-mobile revenue for the first time two weeks ago.

Some people think that Twitter will be more valuable than Facebook eventually, but it’s still worth about one tenth of the largest social network in the world.

(Stock market dropping image via Shutterstock)