Data is Beautiful

Well, that's why you hope that gets controlled with a natural experiment. You can't, for instance, use a control group in a country with different medical policies, but you could have comparable cities and neighborhoods that, arguably, should have similar medical advancements over time. The closer the control group is, the better your validity should be (too bad there's no mirror universe!).

There's a couple other tricks you can use, but honestly my expertise is in education so I'm not sure how widely these are used; Instrumental variables (basically proxies for your target) for instance, like adding property value or something to the model can inadvertently control for things associated with that, like better medical care or infrastructure. You risk over-specifying the model but we have diagnostics that help with that.

(Btw, education, the main concern is there's a billion possible factors in the home, classroom, society, etc, we can't directly capture, so that's how it's used there).