Should we apply PIFs to GBD ylds and ylls

[JDWoodcock]

YLDs: In previous versions we have applied the PIF to deaths, ylls, ylds and hence dalys. Applying them to YLDs is problematic as it does not reflect the longer term change in disease burden because not all the ylls lived will be in full health . It could be seen as indicative of where the benefits occur but not added to ylls to give change in dalys @nmaizlish . This is particularly important for monetising benefits
Thus I see options are

1. we only include ylls
2. we calculate ylds but dont add them to ylls
3. we adjust ylls to reflect likely health status (perhaps using average ylds per age group- as I understand it currently GBD gives incidence ylls and prevalence ylds so i think this should be doable)
4. we adopt some other approach (mulitplier based on Joe Spadaro's approach but this will come with it's own challenges)
5. we move whole scale to PMSLT (probably too difficult for now)

[gotom22]

suggest to specify issue title: this is about "not all the ylls lived will be in full health", correct. Think of a good "working title" for this issue

also pls compare to #21

[markotainio]

I think the main question is whether we can go for PMSLT model in all settings, or not. If we cam, then that will solve the YLD problem. If not, then we need to some scaling parameters, and defining of them would be own (mini)project. Thus, I would propose at this moment to estimate deaths and YLLs.