The no claims bonus in France is expressed in coefficient, and not in percentage. It starts at coefficient 1 as a new driver. The coefficient that is earned is multiplied by 0.95 each year without claim at fault until it reaches 0.50 which is the maximum entitlement.
For instance with a coefficient at 0.72 year 1, it will reach 0.72 x 0.95= 0.68 year 2.
In case of a claim at fault, the coefficient is multiplied by 1.25, for instance with a coefficient of 0.68, the new coefficient further to an accident at fault would be 0.68 x 1.25 = 0.85.
After several claims at fault, it can reach a maximum of 3.50.
The no claims bonus allowance is heavily regulated by government law. They also record any claim you declare, which affects your bonus. If the maximum of 0.50 has been earned for 3 years without any claims, the bonus will not be affected on the next claim.
All insurance companies have to abide with these rules.