Annualised Rate

An annualised rate expresses a change measured over part of a year as the rate it would produce if it continued for a full year. A quarterly output figure reported at an annual rate compounds the quarter's growth four times; a monthly figure annualised compounds it twelve. It is a presentation choice, not a forecast that the pace will persist. The convention differs by country, and comparing across them without checking is a common error: quarterly output is customarily reported at an annualised rate in some statistical systems and as the plain quarter-on-quarter change in others, so the same underlying growth appears as a much larger number in one and a smaller one in the other. Annualising also magnifies noise, since whatever distorted the short period is compounded along with the signal. The release documentation states which convention the headline uses.