The optimal size and structure of government benefit programmes crucially depend on households’ income risk and their ability to self-insure against it. This column demonstrates that in the UK, earning dynamics, such as income risk and shock persistence, differ substantially depending on age and position in the income distribution. Taking these dynamics into account when evaluating benefit policies is of crucial importance, as it dramatically changes the estimated welfare improvements. When the dynamics are incorporated, the 2016 reform of the UK’s benefit system is found to have been welfare-improving on average.