The Fibonacci sequence is a set of steadily increasing numbers where each number is equal to the sum of the preceding two numbers.

If you think Fibonacci was just a crazy Italian mathematician, consider this: The May 2 high at 1,370 and the June 16 low at 1,258 occurred right.

The benchmark index has flirted with - but has so far failed to close above - a key Fibonacci retracement target. Until it does, the downtrend is still alive. Is the S&P 500 index's recent rally ...