I can't say anything about other establishments, but in the subway it, so to speak, works every other time. It happens that you go with a knife in your pocket - does not react, you go with a pneumatic pistol in your backpack - does not react, you go empty (without prohibited items) - questions may arise, although I believe that questions arise in this case not because of the frame.
However, after the frame, when I walked with the knife, they did not stop me.
This is a correct question, but I believe that such statistics (the ratio of the number of people who are stopped for checking, per day to the number of prohibited items found, per day) is not kept by the metro or the Ministry of Internal Affairs.
check the truth or falsity of my thesis, you can apply with a written request to the relevant authorities with the wording of the question I mentioned above.