The answers answered by the previous guy has totally no relevance to what you asked...Sheesh...
Jim Rogers has always recommended Agriculture becos,he is a Commodity guy.His perspective has never wavered from it.
And according to him,its very simple,we have only limited supply of land,food,resources,etc. But bear in mind.Every other second,a baby is born into this part of the universe.Which means to say,that we will come to a point where,food production,resources,may not be able to meet growing demand?Simple economics will tell you the relation between scarcity and price?