I saw some statistic dating from 2007 that stated 131 million tourists had visited China that year. I'd guess that number flew up since then.

The stats of 131 million tourists visited China in 2007 isn't referring to foreigners only. It should be 131 million visitors (person-times) and includes people who travel between HK/Macao and China multiple times or on daily basis. The right figure for foreign visitors (person-times) is 26.1 million in 2007, comparing to 10.1 million in 2000 or 1.74 million in 1990 or 230,000 in 1978.