June 4th was the 24th anniversary of the 1989 Chinese crackdown on the Tiananmen Square protests. The Chinese stock market fell 64.89 points (6/4/89), making a lot of work for the censors. What I'm curious about, however, is how likely this was intentional.

On it's face this sounds unlikely enough to be intentional, but how unlikely is it? Over the last 200 days, Google Finance says the minimum has been -91.85 while the maximum has been 73.68. Naively taking these to be the bounds of possibility and assuming a uniform distribution (good enough for estimating) we get odds of 1 in 16553 of getting -64.89.

This isn't the only outcome that would look like June 4th 1989, however. There's also 64.89, ±46.89, ±89.46, and ±89.64. Having eight special numbers increases our odds by a factor of eight: 1 in 2069. Then there are two other Chinese stock markets, bringing our odds to 1 in 690. The stock market has been running for 21 june 4ths, any of which could have done this, bringing the odds down to 1 in 33.

When we consider how many other significant numbers there are in daily life, any of which could have come out to something readable as June 4th 1989, and especially when we add in the cost of manipulating this large a market, it sounds like this was a coincidence.