I'd like to know which economy sectors in the world are the biggest. Does such statistics exist? If so, how accurate and up to date is it? If not, what can be used instead?
The United Nations Industrial Development Organization (UNIDO) maintains a variety of databases comprising statistics of overall industrial growth, detailed data on business structure and statistics on major indicators of industrial performance by country in the historical time series. The UNIDO publishes the Industrial Development Report 2016 and offers some statistics.
This is one of the most reliable source of industrial data although data are still incomplete for some developing countries.
Broad Sectors: world value added over time. (Source: UNIDO)
Within Manufacturing: In 2013, the dominant global manufacturing indus-tries were food and beverages (12.0 percent), chemicals and chemical products (11.7 percent) and machinery and equipment (8.5 percent; Table 7.2) (source: UNIDO's Industrial Development Report 2016)