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base yearthe initial period from which a system of INDEXATION proceeds. For example, the present UK Consumer Price Index has as the base period 1996 = 100, with the average price of a typical basket of goods in 1996 being taken as the basis for the index. The 2004 index number was 111 for all items in the basket of goods. Convention dictates that the base period always commences from the number 100. See PRICE INDEX.
base (expense) year
In commercial leases, the year used as a measure of a tenant's obligation to pay the pro rata share of ever-increasing building expenses over time.The rent for the first year is usually calculated by the landlord so as to pay currently known building expenses and provide a profit. This is usually the base year. As expenses increase over time, the amount they exceed the expenses of the base year is the figure the landlord uses to calculate the tenant's pro rata share of the expenses.