William O. Douglas

“ All roads operating in Minnesota are taxed on precisely the same, not on different bases. So far as the present incidence of the statute is concerned, the tax is laid on the net credit balances from the business of renting and borrowing cars used in Minnesota. The fact that appellant receives a larger net than others from its Minnesota activity of renting and borrowing cars and hence must pay a larger tax does not mean that Minnesota has overstepped her constitutional bounds. Appellant is not single out for special treatment. ”

“ Certainly the ratio of Minnesota revenue freight car miles to system car miles is consistent with the statutory scheme of ascertaining what payments represent use in Minnesota. That the apportionment may not result in mathematical exactitude is certainly not a constitutional defect. [4] Rough approximation rather than precision is, as a practical matter, the norm in any such tax system. [5]
Second as to the debit balances. As we have said, appellant is not taxed on all of its credit balances but only on that portion which accrues as a result of the use of its cars by others in Minnesota. ”

“ The business taxed is not adequately measured by trackage alone. Though appellant has but few miles of track in the state, nevertheless its cars are constantly moving over revenue. A tax on that revenue certainly bears a close relationship to appellant's property in the state which no computation based on trackage can alter.
As to appellant's second objection under this head, little need be said. Companies not owning or operating roads within the state are not reached by this tax statute; roads that do, are. ”