the DOW dump

On May 6, the DOW dumped almost 1000 points. That's about 10% of its value. That's quite remarkable, eh? So I've been reading that: [1] Somebody typed B (Billion) instead of M (Million). [2] Computers were "in charge" and goofed. [3] Software measured investor sentiment and reacted.       ... and MSNBC was showing video of Greek riots! [4] When traders started selling, there were few buyers.       ... and market orders kept going to low bidders. [5] Proctor&Gamble (PG) dragged down the DOW. [6] Cancelled trades weren't being recorded. [7] Circuit breakers on the NYSE kicked in.       ... so HUGE trading volumes went to other exchanges. [8] Was it manipulation by someone who made a fortune?       (That's from dilbert.) [9] Cyber terrorism. [10] Insert your own explanation. The DOW is proportional to the SUM of 30 stocks prices. How, then, did each DOW component react? What was their drop, from High to Low (on May 6)? They was like so: Figure 1 See? PG dropped the mostest! But does it constitute a large fraction of the Index? Here's the (current) weighting of the DOW 30. Figure 2 See? IBM (with the largest stock price) has the largest weight. And PG? A paltry 4.4%. If'n we take the 30 percentage drops (from Figure 1) and weight them (according to Figure 2), we'd get a 12% drop in the DOW (from High to Low). So ... what's my explanation for the DOW dump? GREMLINS Either that ... or mebbe: