How to enter multi-period average inflation value

[jpfeifer]

See e.g.

Average inflation targeting

Hi APK, Suppose time in your model is a quarter, as it usually is. Quarterly inflation is the defined as the time difference in the log of the price level, such that simply \pi_t=p_t - p_{t-1}. By the same token, annual (4-quarter) inflation is \pi^{(4)}_t=p_t - p_{t-4}. Now, suppose you would like to have a 3-year averaging window. The 3-year (12-quarter) average inflation rate (at an annual rate) in quarter t, \bar{\pi}^{(12)}_t is defined as \bar{\pi}^{(12)}_t=\frac{p_t - p_{t-12}}{3}. Y…