<P> In comparing economic prosperity (using gross national product per person), the British record was one of steady downward slippage from seventh place in the world in 1950, to 12th in 1965, to 20th in 1975 . Labour politician Richard Crossman, after visiting prosperous Canada, returned to England with a: </P> <Dl> <Dd> sense of restriction, yes, even of decline, the old country always teetering on the edge of a crisis, trying to keep up appearances, with no confident vision of the future . </Dd> </Dl> <Dd> sense of restriction, yes, even of decline, the old country always teetering on the edge of a crisis, trying to keep up appearances, with no confident vision of the future . </Dd> <P> Economists provided four overlapping explanations . The "early start" theory said that Britain's rivals were doing so well because they were still moving large numbers of farm workers into more lucrative employment, which Britain had done in the 19th century . A second theory emphasized the "rejuvenation by defeat," whereby Germany and Japan had been forced to reequip, rethink and restructure their economic basic . The third approach emphasized the drag of "Imperial distractions", saying that responsibilities to its large empire handicapped the home economy, especially through defence spending, and economic aid . Finally, the theory of "institutional failure" stressed the negative roles of discontinuity, unpredictability, and class envy . The last theory blamed trade unions, public schools, and universities perpetuating an elitist anti-industrial attitude . </P>

What was the key economic theory of the british empire during the 18th century