Average prices for high-end office investments in San Francisco rose from $180 per sf in 1995 to an average of around $325 per sf this year, according to the study. Of the 35 major office deals closed in San Francisco during the period, six exceeded $400 per sf.

The study also found that investment-grade real estate prices paid through the end of 2004 were not the highest prices paid over the decade, as many might have expected. The Utah State Retirement System-Cottonwood Partner's acquisition of 500 Howard Street, a 10-story, 230,000-sf class A Tower completed in 2003, was the high water mark at about $512 a sf, according to the study. The largest transaction of the last decade was Boston Properties' 1998 acquisition of the 4 million-sf Embarcadero Center for roughly $1.23 billion, or about $307 per sf.

Private investors, including development and investment firms and high-net worth families, were the most active buyers over the 10 years. In San Francisco, however, the office market actually saw a decrease in private owners as a group, while REITs and institutional investors increased their market share significantly, according to the report.