Facebook sees sharp drop in profits 30 January 2013 Last updated at 22:11 Facebook has reported a sharp drop in profits, partly due to increased spending on research and development. The social network site made a profit of $64m (£41m) in the final three months of 2012, compared with $302m a year earlier. Revenue was up 40% at $1.6bn, largely due to a big jump in advertising revenue, a quarter of which came from mobile platforms. Shares in Facebook fell by almost 6% in after-hours trading in New York. The shares launched on the Nasdaq stock exchange in May at $38, and had halved in value by September. They have since recovered to stand at $31 at the close of trading on Wednesday. The drop in after-hours trading suggests the shares will fall back again when full trading resumes on Thursday. "Mobile revenue was expected to be a little higher," said analyst Aaron Kessler at Raymond James. Overall it's a solid quarter but maybe [the company has suffered from] high expectations going into the quarter. Revenue from advertising was $1.3bn, 41% up on a year earlier. Mobile revenue, an important indicator of the company's ability to capitalise on the growing move towards mobile platforms, accounted for 23% of overall revenue. "In 2012, we connected over a billion people and became a mobile company," said Mark Zuckerberg, Facebook founder and chief executive. We enter 2013 with good momentum and will continue to invest to achieve our mission and become a stronger, more valuable company.