> Are residents that much less effective?

Yes, because they aren't yet trained to practice medicine. Residency is where they are trained to practice medicine.

> Do they require so much supervision?

Yes, both by practicality and by law.

> If residents are just cheaper doctors

They're not "just" cheaper doctors

> then hospitals would optimize for a high resident:attending ratio.

They tried. Patients died. Now we cap both the number of hours they can work per week (80 hours/week) and the resident:attending ration.

Oh nice! This is what I'm interested in! What kinds of things can they and can't they do without supervision? What is common in practice? Is there a good place to read about how this all works?

There a black joke amongst doctors in the UK where all the junior doctors start in the same week each year the mortality rates go up :-)

Indeed, and it's not even a joke, but a real phenomenon.

Sources :

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2896592/ https://www.ncbi.nlm.nih.gov/pubmed/21747093

Then ... that means the supervision of residents is not working. That basically means, it's useless. (Since it'd make sense to apply the maximum amount of supervision when a resident is new and as the resident gains trust, decrease it.)

Or of course it means, that attending doctors do a constant amount of (insufficient) supervision, or they ramp up supervision after someone screws up... :|

> If residents are just cheaper doctors

Residents are cheaper doctors, but they are cheaper because they are less trained, less experienced doctors. They aren't equally-capable doctors with lower salary demands.

Sure, but the 90% of problems don't require brain surgery and a consult from a team of specialists.

probably not 90% once your actually admitted to hospital especially if the hospital is a centre for the trickier problems.

Sure, but lots of real problems require more than the skill level expected of residents, if nothing else to have reasonably justified confidence that the problem isn't one which requires more specialized attention.

At that point someone with WebMD and a scriptbook of a random House MD season is more efficient anyway.

But maybe the problem is that if we would have more generalists that'd just shovel more load on the specialists.