It has long been felt by market participants that the one area of the US economy that still has signficant downside is the commercial real estate sector. Just-released data shows that is the case. Accordign to the National Association of Realtors, US commercial real estate activity fell 4.8% in Q1 and fell fell 12.8% from the year earlier. A further decline is expected over the coming 6-9 months, the Realtors say. The office vacancy rate will rise to 16.1% in 2009 from 13.4% in 2008. The retail space vacancy rate will rise to 12.1% this year from 9.7% in 2008.