 On the whole it may be said that Malthus's revolutionary ideas in the sphere of population growth remain relevant to economic thought even today and continue to make economists ponder about the future.In 1799, Malthus made a European tour with William Otter, a close college friend, travelling part of the way with Edward Daniel Clarke and John Marten Cripps, visiting Germany, Scandinavia and Russia.Malthus used the trip to gather population data.