Prediction: These Will Be 5 of the Biggest Stocks by 2040

Although the benchmark S&P 500 tends to head higher over long periods of time, the stocks primarily responsible for pushing the widely followed index to new heights change regularly. As an example, nine of the 10 largest stocks by market cap in 2004 are no longer in the top 10 as of today. In fact, insurer AIG now sits around No. 250 in the market cap rankings.