A weighted average of prices or quantities, where the weights used are the quantities or the prices of the base period. Where pij and qij are the prices and quantities of N goods, i = 1, 2,…N, in period j, and t labels the latest period and 0 the base period, the base-weighted or Laspeyres price index is given by
PB = (Σipitqi0)/(Σipi0qi0)
and the base-weighted or Laspeyres quantity index is given by
QB = (Σipi0qit)/(Σipi0qi0).