In the last twenty years or so,some underdeveloped countries have increased their food production.Their populations, however,have at the same time grown faster,and so their standard of living hasn't improved.What's more,their increase in food production has been achieved at the expense of using up marginal lands.As a result,there has been no gain in the productivity of land labour. • In the last twenty years or so, some underdeveloped countries have increased their food production. Their populations, however, have at the same time grown faster, and so their standard of living hasn’t improved. What’s more, their increase in food production has been achieved at the expense of using up marginal lands. As a result, there has been no gain in the productivity of land labour