a possible maximum World population that can be sustained by Earth's resources, in the year 2072. Commenting on Ravenstein's paper on overpopulation presented at the British Association, the Times, stated that Ravenstein "estimates the population of the world for the present year at 1,468,000,000, and, after making careful allowance for various unfavourable circumstances, he comes to the comforting conclusion that the human race may increase to the number of 5,994,000,000 without outrunning the supply of food". Based on an 8 percent increase of population per decade, "the limit of expansion will be reached in 182 years". "He had estimated the world's population for the present year to be 1,468,000,000. He found that the population of the world every 10 years increased 8 percent. The Total population of the cultivable area would be 5,850,700,000, and the total number which the earth could feed was 5,994,000,000 people". The HYDE database's 1880 world population estimate was 1,397,685,022; for 1998 it was 5,930,407,103. Ravenstein though treated his estimation with indifference and a calm manner. "We fear that we have been seduced into something like levity by the fact that Mr Ravenstein himself does not appear to have been materially shocked and saddened by his own conclusions. Indeed, his closing words indicate a strange spirit of indifference, not to say callousness. So far as we ourselves were concerned, he did not think we need make such a tremendous fuss about it, knowing we would not live to see the day when there was no more room on this earth." Theory of migration He established a theory of human migration in the 1880s that still forms the basis for modern migration theory. The following was a standard list after Ravenstein's (1834–1913) proposal in the 1880s. The theories are as follows: Every migration flow generates a return or counter-migration. The majority of migrants move a short distance. Migrants who move longer distances tend to choose major sources of economic activity. Urban residents are often less migratory than inhabitants of rural areas. Families are less likely to make international moves than young adults. Most migrants are adults. Large towns grow by migration rather than natural population growth. More long distance migrants are male. More long distance migrants are adult individuals rather than families with children. In his book 'Laws of Migration', Ravenstein explained his theory of step migration which sees that migration could be gradual and often occurred