[repelsteeltje]

This immediately gets complicated. I think there is still considerable discussion to be had on what constitutes CO2 emission that can/should/ought to be attributed to a person.

When asked, many people start with: electricity / gas use, car mileage, water use, etc. But beyond eating huge amounts of meat and flying, the number one contributing factor is just stuff. The hidden impact of manufacturing, transport and waste of cloths, electronics, furniture, etc. is number number one in western countries. But it's almost impossible to express that contribution per item.

So buying less stuff is very important, but (other than that meaning money never leaves your wallet) it would be difficult to measure how that contributes to going from 5 to 3 tons of CO2, I'm afraid.