Next come those valuations which depend for their accuracy upon being the true mid-point of probabilities.  A given mine may last for five years in the view of some experts, or it may go on for fifteen in the view of others, and you may take a mid-point, say ten, and collect your tax, but, shortly after, this valuation turns out to be badly wrong, though all your valuations in the aggregate are correct.  While the active procedure of collecting the levy is in progress for a number of years these assessments will simply shout at you for adjustment.  There are other types of difficulty in assessment which involve annual adjustment, but you will appreciate most the necessity for care in the collection.  Enthusiastic advocates for the levy meet every hard case put forward where it is difficult to raise money, such as a private ownership of an indivisible business, by saying:  “But that will be made in instalments, or the man can raise a mortgage.”  But the extent to which this is done robs the levy of all the virtues attaching to outrightness, for each instalment becomes, as the years roll on, different in its real content upon a shifting price level, and every payment of interest on the mortgage—­to say nothing of the ultimate repayment of that mortgage—­falls to be met as if reckoned upon the original currency level.  Then those classes of wealth which are not easily realisable without putting down the market price also require treatment by instalments, and those who wish to put forward a logical scheme also add a special charge upon salary-earners for some years—­a pseudo-capitalisation of their earning power.

A really fair and practicable levy would certainly be honeycombed with annual adjustments and payments for some period of years, and one must consider how far this would invalidate the economic case of the “outright cut,” and make it no better than a high income-tax; indeed far worse, for the high income-tax does at least follow closely upon the annual facts as they change, or is not stereotyped by a valuation made in obsolete conditions.  Imagine three shipowners each with vessels valued at L200,000, and each called upon to pay 20 per cent., or L40,000.  One owning five small ships might have sold one of them, and thus paid his bill; the second, with one large ship, might have agreed to pay L8000 annually (plus interest) for five years; while the third might have mortgaged his vessel for L40,000, having no other capital at disposal.  At to-day’s values each might have been worth, say, L50,000, but for the tax.  The first would actually have ships worth L40,000, so he would have borne the correct duty of 20 per cent.  The second would have L50,000, bringing in, say, L5000 annually, and would be attempting to pay L8000 out of it, while the third would be paying L2000 a year out of his income and still be faced with an 80 per cent. charge on his fortune!  His assessment is computed at one point of time, and liquidated at another, when its incidence is totally different.