The movements of a bilateral exchange rate may be attributed to changing perceptions
and events related to either or both currencies. By looking at a single bilateral rate,
it is impossible to disentangle these attributions. However if we consider the bilateral
exchange rates of one currency against several other currencies, it may be possible to
extract a common component responsible for the generalised movement of the chosen
currency, and it would be of interest to see if this currency-specific component is related
to economic fundamentals for that currency. Multilateral or effective exchange rates
based on goods and services trade weights are routinely constructed in an attempt to
extract a ‘common’ component from bilateral rates. However according to the Bank
for International Settlements in their triennial survey of foreign exchange rate markets,
trade in goods and services account for less than 0.5% of all foreign exchange
transactions globally. This implies that a filter based on these trade weights is largely
irrelevant for estimating the common component of currency movements, particularly
at higher frequencies. Instead, we extract and analyze the principal components of
bilateral exchange rates, which is a filter that accounts for capital as well as goods and
services trades.