 Britain's former age-based policy that once prevented the use of kidney dialysis as treatment for older patients with renal problems, even to those who can privately afford the costs, has been cited as another example.A 1999 study in the "Journal of Public Economics" analyzed the British National Health Service and found that its waiting times function as an effective market disincentive, with a low elasticity of demand with respect to time.Supporters of private price rationing over waiting time rationing, such as "The Atlantic" columnist Megan McArdle, argue time rationing leaves patients worse off since their time (measured as an opportunity cost) is worth much more than the price they would pay.