Causes of income inequality in the US I read an article in BusinessWeek that talked about income inequality in the US.

The article attributed the difference to the Intel chip that came in 1971. Since that time big hi-tech companies have grown in US, which caused income growth among wealthy people and also didn't lead to a relatively large growth in jobs because a lot of work was outsourced to places like China.

To what extent is this explanation valid in the US... or is it insignificant in accounting for the income differences between the rich and the poor?
The reason you bring forward belongs to technological directed change, which is regarded one of the main explanations for wage growth differentials. Keep in mind it's not exactly the way you're phrasing it: The growth in tech companies rewards people who are skilled well for their kind of jobs (as opposed to "wealthy people").

Card and DiNardo have a nice summary article on the issue:


  The recent rise in wage inequality is usually attributed to skill-biased technical change (SBTC), associated with new computer technologies. We review the evidence for this hypothesis, focusing on the implica- tions of SBTC for overall wage inequality and for changes in wage differentials between groups. A key problem for the SBTC hypothesis is that wage inequality stabilized in the 1990s despite continuing ad- vances in computer technology; SBTC also fails to explain the evo- lution of other dimensions of wage inequality, including the gender and racial wage gaps and the age gradient in the return to education.