Adam Smith Quote
The establishment of any new manufacture, of any new branch of commerce, or any new practice in agriculture, is always a speculation, from which the projector promises himself extraordinary profits. These profits sometimes are very great, and sometimes, more frequently, perhaps, they are quite otherwise; but in general they bear no regular proportion to those of other older trades in the neighbourhood. If the project succeeds, they are commonly at first very high. When the trade or practice becomes thoroughly established and well known, the competition reduces them to the level of other trades.
Chapter X, Part I, p. 136 (tendency of the rate of profit to fall). - The Wealth of Nations (1776) - Book I