0 increasing by one addition after another:
The cumulative effect of using so many chemicals on the land could be disastrous.
1 increasing as each new amount is added or as each new fact or condition is considered:
No single development is causing the company’s financial trouble – it’s the cumulative effect of years of weak leadership.
2 increasing by one addition after another, and including all the amounts that have been added before:
We can complete it step by step however long the road is and it can't be completed however short the road is if you don't even mark your footprint.