Percentage of particles bounce off a rigid body

I have particle system w$$anonymous$$ch emits 2000 particles. These particles $$anonymous$$t a rigid body , but not all particles $$anonymous$$t rigid body. Some particles, w$$anonymous$$ch collide with rigid body bounce off and other just flow straight. Out of 2000 particles lets say 800 particles $$anonymous$$t rigid body and bounce off and rest of particles ( 1200 particles) just flow though. So 40% of total particles bounce off. How can I calculate t$$anonymous$$s percentage from the script. Any help or suggestions are welcome.