The ordinary writer should resist the popular novelty of using breakdown in a pseudo-scientific sense vaguely connoting analysis, subdivision, or classification of statistical matter. It is more than usually inept when used of things that can be physically broken down:
The houses erected should be broken down into types. (classified according to type.)
The breakdown of this number of houses into varying densities per acre. (division.)
I should be glad if you would furnish a breakdown of all export orders on hand by countries of destination ; only the total value: of orders on hand received from each country is required. ( a statement of the value of all the export orders you have on hand, showing the total for each country separately.)
Your export figures should be broken down between hard and soft currency areas. (given separately for.)
Averages are notoriously misleading, but even when the figures are broken down in detail, the general impression holds good. (even when the actual figures are examined.)
The Minister wishes to avoid fragmentation of the service by breaking down the two-tier system of administration provided for in the Act into a three-tier system.
Why breaking down in the last example? If the word break must be used at all breaking up would go better with fragmentation. But why not some ordinary word such as changing, altering or converting?
The fascination of this word may lead government departments into the ludicrous:
Care should be taken that the breakdown of patients by the department under whose care they were immediately before discharge is strictly followed. (Classification is presumably meant.)