I imagine they are quite good.
You need to take precautions. Its mostly in big cities and especially in heavily tourist areas. So cities like Shanghai you need to be really careful about when on Nanjing road etc. It happens frequently enough where you must take precautions, but it doesn't feel like its on the level of some cities in Europe where its totally out of control.
We did not have any issues. it's a big city so take care as you would in a big city anywhere.
I have visited Shanghai 4-5 times, never happened to me, but I can imagine there must be many, so be cautious.
Back in late March in Guangzhou, I was on very busy Shangxiaju pedestrian shopping street, a team of 3 pickpockets gathered around me, 2 behind me and moving very close inches from me, 1 detached lookout; my colleagues walking 5 steps away noticed it and rapidly moved up to me and the 2 thieves, within second they spotted it and moved away. We are 3 big guys over 6’ tall. I didn’t know it until it was over.
Haha, the same here, not only for me, but also for everyone I know. They must be very, very bad.
Pickpocketing in the big cities in China is very common. Like in most of the big cities world wide. Luckily is is not extremely bad, as it is in some cities in the world. It is not only limited to tourist sites. I have heard of situations where cell phones were snatched of a table when people were eating.
It is more like: Opportunity makes the thief. So be careful with your belongings, and keep them safe.