There is a website where users contribute articles. User will score points based on the number of articles contributed. The point awarde should not be linear. The point score for each article contribution should diminishes as the number of articles increases.
For example: 1 - 10 contribution will be awarded 1 point each. 10 - 20 contribution will be awarded 0.9 point each. 20 - 30 contribution will be awarded 0.8 point each.
What will be the best algorithm for this?