SAN FRANCISCO -- Google's ( GOOG) innovative paid-search advertising, along with some good old-fashioned belt-tightening, helped it stay healthy during hard economic times. But the question is, how severe do conditions have to get before the company finally succumbs? Most analysts were impressed with Google's ability to grow third-quarter revenue by 31% in the face of a financial crisis, even though it marked a slowdown from its 39% growth in the previous quarter. Shares of Google were up 6.2% to $375.05 in recent trading. A big part of Google's performance can be attributed to its cost containment. The company hired 519 employees in the third quarter, bringing its total worldwide workforce to a whopping 20,123. But that's a much slower clip than a year ago, when Google added 2,130 to its staff. Google Chief Executive Eric Schmidt emphasized on Thursday in a conference call with analysts the need to "keep a very close eye on costs." "It makes sense given everything we read in the papers and we have done that effectively in this quarter," he said. At the same time, paid-search advertising -- Google's main cash cow -- held up well in the third quarter, despite fears that online advertising would contract as advertisers shrank their budgets. Paid clicks, or the number of times a user clicks on an ad, grew 18%, a slight drop from its 19% growth the previous quarter. Sanford Bernstein analyst Jeffrey Lindsay notes that excluding traffic acquisition costs -- or the money that Google shares with its partners -- the company's revenue grew 4% sequentially in the third quarter while its hiring increased by only 2%. That means that Google's staff is working more efficiently, he says.