Has there been an increase in part time labor or disposable labor in the US?

I noticed a high turn over rate where I work. Also I have noticed that some of my previous full time employers are using strictly part time labor because they don't have to pay them any benefits. If this trend is true is it bad news for the labor force? I am talking about semi-skilled and skilled labor. It appears that our work force is being reduced to the level of peasant labor.