Bigger hospitals can afford to have a modest administrative cost because there are fixed (as opposed to variable costs that scale with patients served and departments funded) that scale and amortize in huge organizations. Small hospitals (let's say somewhere in Iceland) either have to do without fancy tech/better staff that usually command more $$$, or have to spend more, increasing their overhead. In reality and to be fair, it's better to compare their patient outcomes and financials in-depth rather than looking at the overhead percentages only.

Your link is provider admin costs. IIRC insurer admin costs are 3% for UK and 5% for Canada.

You're correct; good clarification on which admin costs we're talking about.

Right, I was only talking about insurance administrative costs.