Valuable lessons on NHS policy are being missed as it is nearly impossible to gauge the impact of UK devolution, a report says.
There is an 'alarming' lack of comparable data, the study says
The British Medical Journal report said there was an "alarming" lack of information, blaming the different ways it was collated in the four countries.
Researchers said there were only a few areas of policy where a meaningful comparison could be made.
The team looked at health data from 1996 to 2003.
The study, involving researchers from the King's Fund health think-tank and London School of Economics and Political Science found that, in areas such as NHS spending per person and investment in family health services, it was not possible to do comparisons because of a lack of credible information.
One of the few meaningful comparisons which could be made was on waiting times, which fell in England, but rose in Wales and Northern Ireland.
However, because of the way statistics were compiled in Scotland it was impossible to do a full comparison, the report said.
King's Fund policy director and report co-author Jennifer Dixon said: "There is a major heath care experiment taking place at the moment with all four home nations adopting very different approaches to delivering healthcare.
"This has produced mixed results with England performing better in areas such as waiting times largely as a result of extra money, targets, tough performance management and probably the contestability of clinical services.
"With devolution came an opportunity to learn the lessons from these different approaches, but a worrying lack of information has made this virtually impossible.
"Taxpayers across the UK cannot tell whether their money is being better used in England, Scotland, Wales or Northern Ireland."
Fellow co-author Gwyn Bevan added: "The methods of data collection need to be more carefully designed in order to make the information stand up to scrutiny."
The Department of Health declined to comment.
But a Scottish Executive spokeswoman said attention was given to other areas of the UK when different policies were introduced.
She added: "Health is devolved under the Scotland Act. We are delivering Scottish solutions to Scottish issues."