I'll just throw in my two cents: It seems pretty simple from my point of view. People switch between companies that win bids and contracts. Those companies now

I'll just throw in my two cents: It seems pretty simple from my point of view. People switch between companies that win bids and contracts. Those companies now need to staff and they staff with the people from the companies that lost bids. The people that are picked up happen to know the systems that they're dealing with. Also word gets around to which contractors look "hot" compared to others. They start getting resumes from people looking to jump ship. Combine that with laws that stipulate some amount of contracting money must go to small minority owned businesses... yeah.