The fact that the hide was a unit of assessment, has been established by Mr J. H. Round in his _Feudal England_, and is regarded as throwing a most valuable light upon the many problems which present themselves to the student of Domesday. The process which converted the hide from a unit of measurement to a unit for assessment purposes is probably as follows. Being in general use to denote a large piece of land, and such pieces of land being roughly equal all over England, the hide was a useful unit on which to levy taxation, a use which dates doubtless from the time of the Danegeld. For some time the two meanings were used side by side, but before the Norman Conquest the hide, a unit for taxation, had quite supplanted the hide, a measure of land, and this was the state of affairs when in 1086 William I. ordered his great inquest to be made. The formula used in Domesday varies from county to county, but a single illustration may be given. _Huntedun Burg defendebat se ad geldum regis pro quarta parte de Hyrstingestan hundred pro L. hidis_. This does not mean that the town of Huntingdon contained a certain fixed number of square yards multiplied by 50, but that for purposes of taxation Huntingdon was regarded as worth 50 times a certain fiscal unit.
This view of the nature of the hide was hinted at by R. W. Eyton in _A Key to Domesday_ and was accepted by Maitland. Its proof rests primarily upon the prevalence of the five-hide unit. By collating various documents which formed part of the Domesday inquest Mr Round has brought together for certain parts of England, especially for Cambridgeshire and Bedfordshire, the holdings of the various lords in the different vills, and vill after vill shows a total of 5 hides or 10 hides or only a slight discrepancy therefrom. A similar result is shown for the hundreds where multiples of 5 are almost universal, and the total hidage for the county of Worcester is very near the round figure of 1200. This arrangement is obviously artificial; it must have been imposed upon the counties or the hundreds by the central authority and then divided among the vills. Another proof is found in what is called "beneficial hidation." It is shown that in certain cases the number of hides in a hundred has been reduced since the time of Edward the Confessor, and that this reduction had been transferred _pro rata_ to the vills in the hundred. Thus Mr Round concludes that the hide was fixed "independently of area or value." Some slight criticism has been directed against the idea of "artificial hidation," but the most that can be said against it is that its proof rests upon isolated cases, a reproach which further research will doubtless remove. However, Professor Vinogradoff accepts the hide primarily as a fiscal unit "which corresponds only in a very rough way to the agrarian reality," and Maitland says the fiscal hide is "at its best a lame compromise between a unit of area and a unit of value."