Forecasting inflation is clearly of critical importance to the conduct of monetary policy,
regardless of whether or not the central bank has a numerical inflation target. A simple
Phillips curve, which uses a single measure of economic slack such as unemployment to
predict future inflation, is probably the most common basis of inflation forecasting. The
usefulness of the Phillips curve as a means of predicting inflation has however been
questioned by several authors. For example, Atkeson and Ohanian (2001) found that
Phillips curve based forecasts of inflation give larger out-of-sample prediction errors than
a simple random walk forecast of inflation, although this specific result is very sensitive
to the sample period and to the choice of inflation measure (Sims (2002)). Cecchetti,
Chu and Steindel (2000) consider inflation prediction with individual indicators,
including unemployment, and argue that none of these gives reliable inflation forecasts.
Stock and Watson (2001, 2002a) consider prediction of inflation in each of the G7
countries using a large number of possible models. Each model has a single predictor
(plus lagged inflation). They find that most of the models they consider give larger out
of-sample root mean square prediction error than a simple naive time series forecast
based on fitting an autoregression to inflation. When a model does have predictive power
relative to the naive time series forecast, this tends to be unstable. That is, the model that
has good predictive power in one subperiod has little or no propensity to have good
predictive power in another subperiod