This is A BIT FAR fetched but on CNBC you can see the guys on the NYSE floor with their huge arsenal of 100 200 500 1000 5000 10000 BUY SELL button keyboards and as the very end of the year plunge happened one guy on the floor which is often seen on the CNBC at the background on different days was uncharacteristically incredibly red, totally red, in his face that I knew they were doing it. Guilty person standing right there. Then I just had to wonder why would they do something like that on the floor and try to find a reason. Of course I can be totally wrong but we are at what 16 month highs right at this very minute. If I am proven wrong then people don't have a nice trading tool they can interpret straight from the floor of the NYSE if I am proven right then they do which is nice because who knows better how much money to haul into which direction they have than themselves.
To clarify taking markets down 80 points in 30 minutes is something different ie. requires real effort as seen from the volume, than taking markets down 80 points in an hour or in a day which is normal and insignificant.