Ask HN: Is Silicon Valley in a Boom Cycle?

I've lived in The Valley for 25 years, arriving just in advance of a recession in 1991. Since then, we've had 2 boom cycles (1996-2000, 2004-2007) and 2 major busts in 2001 and 2008. From my perspective, Silicon Valley is currently in a boom cycle: A. Traffic is the worst I've seen [0] B. Multi-story office complexes are going up at an astonishing rate. A drive down 237 and 101 in Mountain View/Sunnyvale/Santa Clara passes more than a dozen major construction sites. And Facebook, Apple and LinkedIn all put up major new HQs in the last couple of years (Facebook just completed, Apple still in progress). C. House prices are surging again. Santa Clara County median price is +11.1% YOY to US$1,000,000 [1] D. Apartments in San Francisco are at all-time highs: Average $4,385 for 2 BR in the city [2] E. The San Francisco Bay Area is now home to 5(?) of the top 20 US companies by market capitalization, including #1 and #2: AAPL, GOOG(L), WFC, FB, CVX. (ORCL have recently fallen out of top 20) F. Unemployment in The Valley has dropped from 7.0% in July 2013 to 4.1% this month [3] If we are in a boom, what are the underlying market factors specific to Silicon Valley, vs. the rest of the US? How sustainable is it? If we are not in a boom, what are the indicators? [0] http://www.sigalert.com/Map.asp#lat=37.55783&lon=-122.138&z=2 [1] http://scc.rereport.com/market_reports [2] https://www.rentjungle.com/average-rent-in-san-francisco-rent-trends [3] http://www.calmis.ca.gov/file/lfmonth/sjos$pds.pdf