Summary Box: LinkedIn impresses with 4Q results

NETWORKING PAYS OFF: LinkedIn Corp. earned $6.9 million in the fourth quarter as its online professional networking service added 14 million members. Revenue more than doubled from a year earlier to nearly $168 million. The results were better than management and analysts had forecast.

THE CATALYST: LinkedIn is playing an increasingly influential role in the employment market as its website emerges as a digital rolodex for headhunters and job seekers alike. At the end of 2011, LinkedIn featured about 145 million profiles.

INVESTORS CHEER: The company’s stock surged almost 9 percent in after-hours trading Thursday after the results came out.