From ZeroHedge, here is a tantalizing story … behind a pay wall. But here is the gist of what I think the article says. Or at least my spin on it.

Here is a chart of US office vacancies nationally (yellow), New York (white), San Franciso (green) and Los Angeles (orange). Note the rapid decline in office vacancies just prior to the financial crisis (often mislabeled as the subprime mortgage crisis). Then look at office vacancies after The Fed's massive monetary experiment of setting rates to near zero and buying a ton of Treasuries, Agency MBS. etc. While San Francisco returned to pre-financial crisis levels of office vacancy, in general the office market never fully recovered.