This is the 2nd of 3 and covers two topics:
1.The impact that certain stocks have on an Index (S&P 500, DOW, NASDAQ, etc.) based on the number of shares a stock has in an Index relative to all others and the “weight” it carries – you can compare this to Congress. Don’t look at the S&P 500 as a bunch of companies, but see it as Congress. In Congress, there are 435 representatives, BUT, not every State has equal representation or voting power, right? The Tiny State of Vermont has one (1) Congressional Representative while across the Country, the Grand State of California has fifty-three (53) – whom do you think carries more “weight” when it comes to Voting and Legislative change? Now, turn NextEra Energy (yep, our old friend FP&L) into Vermont and GOOGLE into California and you begin to see how the outcome of the S&P 500 (Congress) can be effected by one company’s stock. The combined “weight” of the top six (6) represent over 25% of the S&P 500.
2.Computers & Algorithms. I’m in awe of the advancements we’ve made from the power of computers. Add in their operating instructions and you can move mountains (Wikipedia: an algorithm is a finite sequence of well-defined, computer-implementable instructions, typically to solve a class of specific problems or to perform a computation). But, sometimes, left unchecked, this combo can bite the hand that feeds. In September, a textbook example occurred which gives a perfect example.