<human>:  Why isn’t Silicon Valley on the list of high-tech corridors?
<bot>: Silicon Valley is a high-tech corridor, but it isn’t on this list. The list is based on a variety of factors, including the concentration of high-tech firms in a given area, the concentration of high-tech workers in a given area, and the concentration of high-tech companies in a given area. Silicon Valley is one of the most important high-tech corridors in the world, but it doesn’t quite meet the criteria for being on this list.