Globalization is partially to blame for stagnant incomes in developed countries. Free trade has allowed a substantial amount of higher paying manufacturing jobs to be outsourced to low costs countries. This has resulted in stagnant wages for many workers. However, technology has also played a role in the lack of wage growth too. Therefore, a combination of globalization and technology have hurt wages for many in developed countries.
Many people extol globalization as a cause for increased interactions and the faster spread of ideas. However, it has also caused economic collapse as countries see their GDP run out the door to sponsor activity elsewhere instead of keeping those funds close to help local infrastructure, which has resulted in more economic stagnation.
As trade between developed and developing nations increases, the balance of wages and Per Capita Income between first and third world counties will change. This leveling of the playing field is one reason why incomes in developed countries are starting to stagnate. The gap will only continue to get smaller.
There are thousands of factors that can influence income levels. Although many people have seen their income levels fall, I don't believe that this is the result of globalization. It is true that the economy in one area of the world affects others, but I think blaming globalization is too simple a solution.