The Wealth of Nations by Part 4 Chapter 7 Page 135

In those other branches of trade it has diminished the competition of British capital, and thereby raised the rate of British profit higher than it otherwise would have been. On the contrary, it has increased the competition of foreign capitals, and thereby sunk the rate of foreign profit lower than it otherwise would have been. Both in the one way and in the other it must evidently have subjected Great Britain to a relative disadvantage in all those other branches of trade.

The colony trade, however, it may perhaps be said, is more advantageous to Great Britain than any other; and the monopoly, by forcing into that trade a greater proportion of the capital of Great Britain than what would otherwise have gone to it, has turned that capital into an employment more advantageous to the country than any other which it could have found.