The Disability Adjusted Life Year does a pretty good job in measuring welfare improvement. When used for multiple interventions, it gives us a bird's eye view of cost effective interventions.
The tradeoff is that some donors may find this bird's eye view very broad. For example, the Cost/DALYs averted can tell you about cost effective interventions, but it cannot give context on the nature of welfare improvement, or help you rank which improves welfare the most.
And it's because there is no universal way to do so, the context varies. For example, do you value an intervention that eliminates chronic debilitating suffering in an adult over one that prevents neonatal mortality? Or vice versa?
These are philosophical questions with no single answer.
Organizations like Givewell think deeply about such questions. So the DALY isn't a core impact metric for them. Instead, they use different welfare measures like life years saved, extreme misery averted, adult lives saved, and so on.
