But it is evident that the variation in different states, between the food and the numbers supported by it, is restricted to a limit beyond which it cannot pass.

In every country, the population of which is not absolutely decreasing, the food must be necessarily sufficient to support, and to continue, the race of labourers.
Other circumstances being the same, it may be affirmed that countries are populous according to the quantity of human food which they produce, and happy according to the liberality with which that food is divided, or the quantity which a day's labour will purchase.

Corn countries are more populous than pasture countries, and rice countries more populous than corn countries.

The lands in England are not suited to rice, but they would all bear potatoes; and Dr Adam Smith observes that if potatoes were to become the favourite vegetable food of the common people, and if the same quantity of land was employed in their culture as is now employed in the culture of corn, the country would be able to support a much greater population, and would consequently in a very short time have it.
The happiness of a country does not depend, absolutely, upon its poverty or its riches, upon its youth or its age, upon its being thinly or fully inhabited, but upon the rapidity with which it is increasing, upon the degree in which the yearly increase of food approaches to the yearly increase of an unrestricted population.

This approximation is always the nearest in new colonies, where the knowledge and industry of an old state operate on the fertile unappropriated land of a new one.
In other cases, the youth or the age of a state is not in this respect of very great importance.