Given that Technology has the largest weighting in the S&P 500, it comes as little surprise that four of the ten largest companies in the index are from that sector. While most would expect to see MSFT near the top of the list, AAPL is currently the fourth largest company in the S&P. The stock that was left for dead a little more than ten years ago now has a larger market cap than JPM, PG, JNJ, GE, and IBM. A couple more good days and Apple will also be bigger than Wal-Mart (WMT)! GOOG is another name in the top ten that wasn't even in existence ten years ago.
The list of largest companies also illustrates the top heaviness of the index. With a total market cap of $1.98 trillion, the ten largest names represent just under 20% of the total market capitalization of the index. Their market cap is equal to the combined market cap of the smallest 321 companies in the index!