State the Price level and time

We are rarely interested in the value of price level at a specific point in time. What we are interested in is percentage change in the price level between two points in time.

We calculate percentage change by first creating a basket of services and goods. At regular intervals (generally once a month on the first day of the month) we measure all prices of the contents of basket (mainly as an average of market) and calculate price level. In this manner, we will end up with a time series of price levels - one value for every month.