Business networking site LinkedIn has recorded a healthy return on its investments, recording over 100% growth in revenue for the fourth quarter year-on-year.

According to today’s earnings report, the site pulled in US$167.7 million for the three months to December 31, compared with US$81.7 million for the same period in 2010.

Net income was up 30%, from US$5.3 million to US$6.9 million, and the site now boasts 150 million members.

Shares were up 9% in after-hours trading, suggesting the results may finally have given investors confidence in the company. Since its IPO in May, shares have fluctuated as high as $109.97 and as low as US$59.07; their current value is US$83.53.

Steve Sordello, CFO of LinkedIn, says the results underscore the company’s success in 2011.

"In 2012, we will continue to invest in our product, engineering, and sales infrastructure to capitalise on our long-term opportunity,” Sordello says.