Each time the CPI is revised, the new series is calculated using a new regimen and a new set of expenditure weights. This is linked to the old series to form a continuous long-term series by chain-linking. The new index is given a base value of 1000, and all index numbers based on the superseded regimen are scaled to the same base as the new (revised) index. eg If in the rebase year the existing index was 1350, then this figure would be reset to 1000 by multiplying it by 1000/1350. All existing index numbers based on the superseded regimen would be adjusted by this same link factor.