Probably quite a few, but it's more likely most people don't bother trying to considering the process to enter the CPC is fairly strict; if I remember you have to undertake rigorous party study sessions, pass examinations and background checks, and have an existing party member be your mentor throughout the whole process. And this can take at least several years before you're finally admitted.
According to this SCMP article around 32 000 people left the CPC in 2010, but the party official who quoted this number didn't give a breakdown of it.
I imagine lots of Zionist pants were shitted in in the last month.