How freely resources flow is determined by resource.trade.effect , a function of Lateral . N is greater than GNP . S , then Lateral . S is greater than GNP . N , then Lateral .
Pressure is negative.
Note that because the initial values of GNP . N and GNP . S are equal, the initial value of Lateral . Pressure is 0. Pressure then drives resource.trade.effect as shown in Figure 53 .