Estimates of the ratio of annual sales to expenditure on research and development are difficult to make in respect of the undertakings active in the field covered by this chapter, partly because of the large number and variety of those undertakings, 연구와 개발에 지출하는 연간 매출의 비율의 견적은 하기 어렵다.? ㅠㅠㅠㅠ
and partly because much of the research and development expenditure is not known to those outside the firms concerned.
Estimates of annual sales can be made from publicly available figures in some better-established parts of the field.
Total hip replacements are now performed in Great Britain at the rate of tens of thousands per year; the prostheses themselves cost between about £25 and £80 (those containing polyethylene being cheaper than the all-metal designs); so the cost (borne largely by the taxpayer) of the prostheses alone is not less than half a million pounds a year, and probably more.
The number used seems certain to increase during the next few years, as does the export market; in the U.S.A.. there are roughly ten times more orthopaedic surgeons than in the U.K., which gives an idea of the potential market there, of which British exports ought to take a share.
About 4000new patients are fitted with artificial legs each year in England and Wales; if each patient is provided with two legs, at a charge to the National Health Service which can be assumed to be in the region of £100 each, that means an annual payment of £800 000 to the leg manufacturers (who, with one exception, are owned by one industrial group).
Of course, there are also established limb-wearers whose legs need replacing at intervals, and the total charge is thus considerably greater than the figure estimated above.