On Tuesday Google's stock price broke the $500 barrier for the first time as analysts predicted the stock may yet gain another 20 percent.

Google joins a group of six companies with shares trading above that level, including Berkshire Hathaway and Washington Post Co., reports Bloomberg. Google began trading at $85 a share in August 2004 and reached $400 a year ago; its shares have soared 22 percent this year. Google's market value is now more than $155 billion, behind Microsoft and Cisco Systems among U.S. technology companies. Yahoo is worth about $37 billion.

Google has beaten analysts' profit estimates in all but one of its nine quarters as a public company. It is now valued at 62 times earnings, Yahoo's stock trades at 55 times earnings, and Microsoft at 22.9 times, according to Bloomberg data.

"Expectations for the online advertising market overall remain very robust," Sasa Zorovic, an analyst at Oppenheimer & Co. in Boston, is quoted as saying.