There were 284 tax-payers in Howden in 1379, made up of 133 couples and 151 single people for a total of 417 adults aged 16 or over. To get an accurate figure for the overall population, we need to estimate the number of children under 16 and make an allowance for tax evasion and exemptions for poverty.
Estimates for the proportion of dependent children at this time vary between widely between one-third and a half of the total adult population. The one-third proportion would give us 139 children, so assuming no single person had children, and that some couples either had no children or had only adult children, we would have around 1.5 - 2 young children per family. Using one half would give us 208 young children. or about 2.5 per family. The total population at this time was either static or actually falling, so I would favour the lower figure, giving us a total population of 556.
An alternative suggestion is to multiply the figure by 1.9, giving a total of 792. However, these would mean there 375 children under 16, divided by 133 couples to give almost 3 children per couple. With some couples having none, this would raise the average to well over 3 living children per couple, which seems much too high.
Tax evasion rates of between 5 and 25% have been suggested. However, these were for the 1377 tax, where wives were taxed at the same rate as their husbands. In 1379 wives were not taxed, so there was less need (and less chance) of evasion. Howden was an actively governed town, and it's hard to believe many potential taxpayers would have been omitted. Exemptions for poverty are even harder to estimate, but with presence of the clergy at the Minster and the Bishops officials at the Manor House there should have been a chance for everyone to make a living. However, there may have been widows living with sons or daughters, and adult children working the family land who had no income and would therefore not have been taxed.
Taking all these factors in consideration, it seems reasonable to suggest the total population of Howden in 1379 was 550-600, with a preference for the lower figure.
How did Howden compare with other towns? Although few returns have survived for 1379 for East Yorkshire, we do have the 1377 results. Couples were taxed twice, so we can compare the 1377 tax-base with the 417 total adults in Howden. The fact the minimum age had gone up from 14 to 16 in the intervening two years suggest the same lists were used for both taxes. Comparing the parts of Howdenshire where we have figures for both years, 1377 totals 610 and 1379 621. This does suggest a certain amount of evasion in 1377, as the 1379 figure would expected to be smaller - no-one had been added, and some tax payers would have died between the two taxes. However, it's also possible that new tax-payers had moved into the area, so on balance we can say that the two sets of figures are roughly comparable.
Allowing for the fact that the 1377 figures may under-estimate the population due to evasion, we can see how Howden compares with other towns in the East Riding:-
Town 1377 1379
Not only does this place Howden as the fourth largest town in the riding, but it's the largest without a large mercantile population. For reasons why this was so, see the page Urban or Rural.