FRED is the tool that allows you to check an economic figure for yourself instead of taking it on trust. It contains series on prices, wages, exchange rates and employment, published by American and international statistical agencies — and you can chart, compare and download without an account or subscription.
It is notably through it that the exchange rate checks needed for any conversion are carried out — those required, for example, to read the Big Mac Index, or to compare an amount in francs from the 1990s with its present-day equivalent.