(PP's statistics sound weak because people banging as much as our two would likely have higher consequences from condom failure than those banging once every week or so. Another site said that 0.01 Polyurethane condoms had a ~3% to 8% breakage/slippage rate vs the thicker standard latex ~1% to 2% rate.)
According to Planned Parenthood:
If you use condoms perfectly every single time you have sex, they’re 98% effective at preventing pregnancy. But people aren’t perfect, so in real life condoms are about 87% effective — that means about 13 out of 100 people who use condoms as their only birth control method will get pregnant each year.