Dell just rejoined the S&P 500. In addition to earnings reports, another notable event that occurs each quarter is the rebalancing of the S&P 500. Companies must meet a number of criteria before they're eligible for inclusion in the index. If companies do not maintain these protocols after joining the index, they risk being replaced. Dell Technologies (DELL -4.96%) officially rejoined the S&P 500 in September. It's important to note, however, that Dell did not fall out of bounds with the S&P's criteria. Ins ...