"Sleepwalking Into An Even Worse Version Of The 1930's Depression"
Authored by Gail Tverberg via Our Finite World blog,
World GDP in current US dollars is in some sense the simplest world GDP calculation that a person might make. It is calculated by taking the GDP for each year for each country in the local currency (for example, yen) and converting these GDP amounts to US dollars using the then-current relativity between the local currency and the US dollar.