On the 4/26 show, someone called in to complain about the switch from GNP to GDP, saying GDP is no good and GNP is great.
Frankly, I see no difference
GDP - how much stuff is produced in the US (includes Toyota plant in California)
GNP - How much stuff US nationals/corporations produce in the world.
Clearly, GDP is the preferred measure, but it turns out there's not much differenence over time. GNP is less than GDP, but it doesn't appear like there's a big change over time.