I think job hopping happens for the same reasons layoffs do: short-term thinking on management's part. I've been an engineering manager for 8 years now and hav

I think job hopping happens for the same reasons layoffs do: short-term thinking on management's part. I've been an engineering manager for 8 years now and have observed that a) giving an external candidate a $10-15K bump during negotiations is fairly easy while b) giving that same bump to an existing employee is practically impossible. Engineers learn that moving every 2-4 years is the way to keep their salary growing, while the same companies that claim to not be able to pay them more happily dish out even more money to hire their replacements.