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others, should be a major objective of this, as any other,research, and it happens that the very topics (mainlyhazards, therapeutic and environmental) that the case-control method is often used for are those about whichimmediate public concern is predictable and legitimate.Cohort studies of environmental carcinogenesis, for

example, would take many years, and a randomisedexperiment would be impossible.

Almost everything that worries research-workersabout case-control studies can be found in one example.The reserpine/breast-cancer saga is as puzzling now asit was when it began five years ago, and it is no wonderthat one of the liveliest of the discussions in Bermudacentred on Darwin R. Labarthe’s review of this contro-

versy. Editorially, The Lancet was able to switch froma verdict of guilty to not proven very quickly, a changemade possible by the speed with which case-controlstudies can be mounted. Holes can be picked in the de-sign of the original studies but no-one has made a breachwide enough to endanger the fabric. This is disappoint-ing, for an explanation of the reserpine anomaly wouldhave enhanced the reputation of case-control studies inclinicians’ minds and gone a long way towards clearingup similar problems, oestrogen-replacement therapy andendometrial carcinoma being a topical example. Somepoints did emerge, however. First, there was the recogni-tion that programmes such as the Boston one on drugsurveillance should be hypothesis generating, not

hypothesis testing. Then, following OBL from this, there. is the need for confirmatory studies to be wholly inde-

pendent : the Boston, Bristol, and Helsinki series wereneither one nor the other. Then there is the matter ofcontrols--obvious, perhaps, but still capable of castingdoubt. Do women who have experienced vaginal bleed-ing make very good or very bad controls for studies ofendometrial carcinoma? There is also room for researchinto the research method itself. And what does one makeof David L. Sackett’s list of thirty-five possible sourcesof bias? In drawing up the rules of the game epidemiolo-gists should not forget that clinicians, not without rea-son, get sceptical of a study size of a few dozen whittleddown from a population base of thousands.

. The case-control study is here to stay, and some of itsfiercer critics seem to be mellowing. As for reserpine,there is little justification for going beyond the conclu-sion that a weak statistical association is valid but un-

likely to be one of cause and effect. Maybe the failureof the Bermuda symposiasts to clarify the reserpinework is not so disappointing after all: if confusion canreign after eleven more-or-less sound case-control

studies, there will not often be justification for any drugor other agent to be banned on the basis of one.

CHOICE IN THE MEDICAL MARKET

THE Institute of Economic Affairs is hardly to beplaced among Britain’s left-wing rowdies. Its title sug-gests an academic and detached stance. It is pronouncedto be "independent of any political party or group".Created in 1957, it is defined as "a research and educa-tional trust that specialises in the study of markets andpricing systems as technical devices for registering pre-ferences and apportioning resources". Many of its utter-ances have been less than enthusiastic for Stately wel-

fare. Its shrewder contributions have been well worthyof debate; its less persuasive pronouncements have scar-cely called for powder and shot. Only modest artilleryneed be ranged against Over-Ruled on Welfare,’ a newand opportunely post-election book by the Institute’s

general director, Ralph Harris, and its editorial director,Arthur Seldon. It is a none-too-scientific elaboration ofthe results of four questionnaires (conducted in 1963,1965, 1970, and 1978), which were designed to assessthe knowledge and preferences of British citizens about(among other things) what the State provides or mightoffer "unpriced" in health care and in education com-pared with the potential of the "priced" private sector.The Institute’s results are interpreted as meaning that

between 1963 and 1978 approval for the post-1945 uni-versal provision of tax -financed services fell from 42%to 22% in health and from 52% to 16% in education.Over the 15 years, support for individual choice in "con-

tracting out" was found to have risen from 34% to 58%in health and from 28% to 65% in education. No doubtthese figures indicate some trends in public opinion as-sociated with what Harris and Seldon call the embour-

geoisement of the working classes, but the surveys weretechnically unsound. They sometimes asked two thingswithin one question and the responses were thereforemuddled; and the representativeness of respondents wasfar from satisfactory, because pensioners were excluded(inquiries were limited to "family decision-makers").The key sociological issue is whether or not the respon-dents had a clear understanding of the implications ofthe questions. There is no evidence that they had. Thebook scarcely mentions any practical experience of thefree-choice market which is the Institute’s Mecca. The

high bureaucratic cost of private health insurance2 is

ignored.The results of these protracted inquiries do illustrate

how poorly these samples of the British public were in-formed about the distribution of Government expendi-ture-as a whole and within each sector. An "averageguess" about the national cost of unemployment benefitwas ,20 for every ;100 of public expenditure ratherthan the true 1978 figure of 2. If, as the Institute’s di-rectors argue, their data are an important reflection ofattitudes and preferences, why do they disregard one oftheir chief findings-the unpopularity, among those

questioned, of defence expenditure? The book providesthe champions of the free market in health care withanother opportunity to state their beguiling case for thereplacement of Government control and support bycompetitive private health insurance and tax reforms.Though they accept the chance with gusto, their health-care argument remains unattractive simply becauseability to pay seems to be given more weight than medi-cal need. The wider acceptance of these views coulc

damage one of the country’s most respected and now ail-ing traditions, the National Health Service. At a timtwhen restraints in public expenditure are prominent irthe Government’s plans, these diversions created by thtInstitute of Economic Affairs must not be taken as an)justification for allowing the N.H.S. to drift downwardsundersustained by funds from general taxation.

1. Over-ruled on welfare: the increasing desire for choice in education andmedicine and its frustration by ’representative’ government. By RalphHarris and Arthur Seldon. Hobart paperback no: 13. London: Instituteof Economic Affairs. 1979. Pp. 249. £3.

2. Lalonde M. Beyond a new perspective: 4th annual Matthew B. Rosenhauslecture. Am J Public Health 1977; 67: 357-60.