Where Have Silicon Valley's Middle Class Jobs Gone?

I have to admit I wasn't surprised to read earlier this week that Silicon Valley is losing its middle class jobs at a high rate. From my own (admittedly) non-scientific perusal of housing prices ($900,000 for a 700 square-foot home is considered a good deal in Palo Alto) and rent prices (which have gone up an average of 10% over the last year, putting most 2-bedrooms over the $2000 mark), I have decided that this must be one of the most inhospitable places in America for middle-class wage earners. According to the 2008 Silicon Valley Index, which tracks employment, growth and income trends in the region, a two-worker family needs to earn $77,076 just to make ends meet. Although I know that the Valley has higher per capita income than anywhere else in the country and is generally defying the rest of the nation's economic slowdown, you've got to wonder what's happened to the 50,000 middle-class jobs that disappeared between 2002 to 2006. While there's been more growth at the top-paying professions, there has also been growth at the bottom as well, which may be a troubling indication of the beginnings of a bifurcated labor market.