(BTS) With BTS the GNP takes on a different meaning. In fact it becomes an indicator to the overall prosperity of a nation rather than just an indication of how much commerce tiles are being worked. This makes it more useful in judging how well a nation is off, because to get a high GNP you need to have improvement in all areas to generating extra commerce, research, culture and espionage. However since the research bonus is added into the figure it is more sensitive to changes in research level then the other three. The only problem with it measuring 4 factors instead of 1 is that you don’t know the proportion of the contribution of each to the value, but i guess that is what your spies are for.