| A numerical illustration of increased complexity is that when the Central Statistical Administration in 1959 drew up what is called an input-output matrix (or table) for main products, this covered 65 industrial sectors or branches and nearly 200 products ; but the official industrial nomenclature list of 1960 contained as many as 15,000 product groups. The “system of balances”  (which is crucial to planning methodology) operated before the war with some 400 to 500 items and today with something in the neighbourhood of 1,500 — and even these cover less than half of all output in value. This number of balances could scarcely be calculated and re-calculated in the time available without the aid of electronic computers. Similarly in Poland the number of products included in the system of balances is between 400 and 600. In the pre-war dozen years alone about 9,000 new large-scale Soviet industrial enterprises were put into operation. In the single year 1963 more than a thousand new large-scale industrial enterprises entered upon activity ; and in total the Soviet Union today has more than 200,000 State enterprises. In a country like Czechoslovakia the number of centrally approved planning targets by 1953 (though they were reduced later) had reached a total of 2,251, and the number of centrally allocated goods as many as 974. It is said to produce today all-told a million and a half types of output !
 A “balance” for a product consists of all the uses for it listed on the one side, and all the sources of supply of it on the other. Thus it can be thought of as an equation of supply and demand. Whenever a plan target is altered, all the relevant balances have to be recalculated and supplies or uses readjusted to secure a new “ﬁt”. The repercussions of an initial change may be very extensive ; but the time-factor usually limits the area over which recalculation is possible.