World GDP in current US dollars seems to have peaked; this is a problem

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.

To get a world total, all a person needs to do is add together the GDP amounts for all of the individual countries. There is no inflation adjustment, so comparing GDP growth amounts calculated on this basis gives an indication regarding how the world economy is growing, inclusive of inflation. Calculation of GDP on this basis is also inclusive of changes in relativities to the US dollar.

What has been concerning for the last couple of years is that World GDP on this basis is no longer growing robustly. In fact, it may even have started shrinking, with 2014 being the peak year. Figure 1 shows world GDP on a current US dollar basis, in a chart produced by the World Bank.