By Abearica Online Editors · Published
Before comparing GDP figures, copy the complete series name, currency unit, price basis, and year. Only then decide whether the figures answer your question. Treat two charts as separate evidence until you have checked that their measures match.
The World Bank explains that current-price data use the prices of the particular year being measured.3
Constant-price series instead express each year in the prices of a chosen reference year.3
Decide whether you are comparing across time
Current-price series are affected by inflation, while constant-price series adjust for price inflation to measure volume growth.3
For a question about growth over time, look for the price basis before describing an increase as a change in output. Keep the source's own definition with the chart. Do not join the end of one series to the beginning of another because their lines appear to meet.
The Bank says its constant-price US-dollar series preserve the growth rates reported in constant local-currency series.1
When a chart in News uses dollar figures, check the underlying series rather than supplying a currency interpretation from the headline. If the chart does not identify the measure, leave the comparison unresolved.
Do not silently swap international dollars for US dollars
An international dollar represents purchasing power comparable to that of a US dollar in the United States.2
The World Bank associates that term with purchasing power parity, or PPP, data.2
Copy "international dollars" in full when that is the unit. Do not relabel it simply as dollars in your own table. For a longer comparison, use Research & Learn to keep definitions beside the figures.
Leave yourself an audit trail
Before sharing the table, read its column headings aloud as complete descriptions. Include the measurement year in those headings or in an adjacent note, and leave empty observations empty rather than substituting a nearby year without explanation.
Save the source, observation year, series name, and reference year together. Keep any question about what the figure leaves out in a separate note. If you are planning through Travel, check actual trip costs independently instead of turning a national GDP comparison into a personal budget.