Immigration policy is also a huge factor in the supply side. Lazy enforcement on illegal immigration has put the squeeze on the lower end of the income spectru

Immigration policy is also a huge factor in the supply side. Lazy enforcement on illegal immigration has put the squeeze on the lower end of the income spectrum, while some visa programs were designed specifically for the purpose of keeping higher end workers wages from increasing. Then you've got NAFTA and other trade policies that have had an impact as well.