The mark-up may vary cyclically, but the major source of cyclical rise in inflation is via a cyclical rise in costs, primarily through cyclical increases in wage costs, in turn due to demand pressure in the labor market. The firm passes forward such increases in costs. The real action is in the labor market.
Median: This procedure computes price change for all the commodities, arrange them in ascending order, calculate cumulative weight of the new series and take the inflation of the first commodity for which cumulative weight is greater than or equal to 50 per cent.