I think the slope is the whole point of the graph and it is supposed represent efficiency although in a very unfortunate way. The angle of the slope is defined by arcsin((life_expectancy - healthcare_costs) / constant). It's a bit like subtracting apples from oranges.
If there's one thing I've learned at engineering school it's that mixing up units of measurement is not a good idea. If you subtract years from dollars the value you get will carry no meaning. And that's why this visualisation is completely meaningless. They should come up with a more clearly defined and sane approach.
If there's one thing I've learned at engineering school it's that mixing up units of measurement is not a good idea. If you subtract years from dollars the value you get will carry no meaning. And that's why this visualisation is completely meaningless. They should come up with a more clearly defined and sane approach.