According to blockchain.info, the current dominant mining pool is Foundry USA which has 33.55% of the global hashrate
- Hashrate percent: 33.55%
- Confirmations > Reorganization risk: 1> 68.99%; 3>41.73%; 6 > 21.31%
His numbers are actually a little off.
For 33.55% of the hashrate, the probability an attacker is successful after 1 confirmation is 70.12%, after 3 confirmations is 43.54%, and after 6 confirmations is 23.09%.
On closer
examination of the code here, it seems the error is that his calculation is not taking in to account fractions of a percent. You can test this yourself by putting in the hashrate box, for example, 30 and 30.999, and seeing they produce the same result.