Five stocks delivered half the S&P 500's gain from April 1 through May 6. Alphabet, Nvidia, Amazon, Broadcom, Apple. Together they added 6.6 percentage points to a 13.5-point index move. The other 498 names combined for the other 6.9. 1% of the index did 49% of the work in 35 days. The average top-5 stock contributed 1.32 percentage points. The average everything-else stock contributed 0.014. The leaders moved the index 94 times harder than the median name. Four of the five are pure AI…