Health Insurance Company UnitedHealth Group will be replacing Kraft Foods on the Dow Jones Industrial Average. The switch will happen at the start of trading on September 24th.The Dow Jones Industrial Average is an index of 30 public companies and what they did during a trading session in the stock market. The index is often used to judge the state of the stock market in general.Kraft Foods was added to the average four years ago in 2008, when it took AIG’s spot on the index. The replacement will not affect the level of the index, which is nearing a record.