what the lamda mean in this equation here? some form of fraction?please try and also try to explian the equation as well.

One argument, which is sometimes made, is that poor countries are poor because they are overpopulated. This argument makes no sense in our model because the production function has constant returns to scale in capital and labour. In the long run, the capital stock will adjust to the size of the population so that all countries have the same capital stock, and the same production, per worker. To make sense of the overpopulation argument, we must introduce some natu- ral resource such as land into the production function. Suppose that we have the following production function: Y =Kazi (my-amt ' where Z is land, which we take as a xed factor which, contrary to capital, cannot be produced. Dividing by N we get production per capita: =()\"()'Er' where A > 0. Now, production per capita depends not only on the capital stock but also on the amount of land per capita. A country with little land per capita will be poorer and a country with much land will be richer. In practice, however, agriculture constitutes a small share of the economy in rich countries. As we saw in Chapter 1, production in agriculture constitutes only 1-3 percent of GDP in the richest countries. Also, differences in population