What would have been the value of sheep's wool in the viking age Scandinavia and England in terms of silver or other goods? And how much wool would a sheep have produced in a year? How big would the flocks have been? And what kinds of textiles would have been produced from it? Was English wool exported to Northern Italy even then?
Researchers suppose that plain woolen textile, called Vaðmál in Old Norse, was used as a kind of currency in Viking Age and medieval Iceland where the island lacked enough circulation of minted coin issued by the rulers, though to what extent this kind of economy in kind was still prevailed especially in medieval (post- Viking age) Scandinavia has just been heavily disputed [in the 21th century] among numismatists.
Gelsinger's classic monograph on medieval Icelandic economic history summarizes some basic conversion formulas between the silver weight and the basic measurement unit of Vaðmál mainly based on Grágás, Icelandic lawbook (Gelsinger 1981: 33-44).
In the Icelandic lawbook, Vaðmál of six ell/ alnir (about 46 centimeters long for the short öln (singular form of alnir, ell)) long and two alnir, thus 276 centimeters long and 92 centimeters width, is counted as a standard legal monetary unit, one Icelandic eyrir (1 eyrir=27.125g; aurar in plural form). Signs to measure 20 alnir is also said to have carved on the wall of the church stood at Þingvellir in Iceland.
The exact conversion ratio between this legal eyrir and actual silver in Iceland apparently fluctuated in course of the Viking Age and after, however (Gelsinger 1981: 35-37). Gelsinger also lists that the ratio between the legal eyrir and the same weight of pure silver (valued twice as impure one) changed from 2:1 to 10.83:1. Thus, 1 eyrir Vaðmál could be exchanged with about 2.5-13.5g of pure silver - either with 5-27g of impure silver.
1 "Ell" (öln) was apparently a bit longer (about 49cm long) in medieval Norwegian law book (Older Gulathing Law), but the basic conversion ratio (1 eyrir/ ora in Old Norwegian vs 6 ells) was the same as the stipulation in Icelandic Grágás (Smith 2019: 254).
Norwetian Older Gulating Law and other documentary records also set the standard price for a cow (not older than 8 years old - and could probably produce enough milk) as 2 or 2.5 eyrir (about 54-67g) of pure silver (Gelsinger 1981: 37f.). This price of cow (called kúgildi in Old Norse) was also fairly common standard unit of money/ value in early medieval northern Europe, and you can compare it with the price of Vaðmál.
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Unfortunately, while Æthelstan's Grately legal codex does provide a value for a sheep (one shilling), it doesn't provide us with the value of its fleece. If we go back to the early 8th Century, cap. 69 of the law code of Ine of Wessex declares that:
- A sheep shall retain its fleece until midsummer. If it is sheared before then, 2 pence shall be paid for the fleece.
It's worth noting immediately that this is not a market price but a punitive one. Outside of vague attempts at price regulation by Edward the Elder that were quickly relaxed by Æthelstan (and even these were 'generic' livestock values more for the purposes of commerce taxation than they were attempts to 'fix' prices), English kings generally refrained from interfering too heavily in economic matters beyond trying to establish fair exchanges for things like labour and communal use of burden animals. In short, then, the two pence stipulated by Ine is a punitively low price presumably designed to dissuade farmers from shearing early and trying to flood the market early with underweight fleeces. While we don't have any contemporary values for the worth of wool, Christopher Dyer (Standards of Living in the Later Middle Ages, 1989), suggests that in 1380, "best wool" could sell for around five shillings per yard.
This unfortunately doesn't give us a particularly definitive answer, as the amount of woolen yarn or woven fabric that can be produced from a fleece depends heavily on the weight and quality of the fleece. The British Wool Board states that both ancient British breeds like the Badger-Faced Welsh Mountain and breeds introduced by the English or contemporary Britons like the Shetland, or breeds introduced in the 9th and 10th centuries like the Herdwick on average produce fleeces of 1.5-2kg, although the finer wool of the Shetland produces a lighter fleece of about 1-1.5kg. And while the fine wool of a Shetland or a Soay is excellently suited for soft, silky high quality fabric in luxurious clothing, the medium fleece of the Welsh Mountain is notably coarser and as a result would produce a somewhat rougher fabric (albeit one that would still be perfectly wearable and affordable for most of the population), whereas the Herdwick produces a very harsh and coarse fleece that would be suitable mostly for blankets or cheaper outer clothing such as mantles or cloaks.
We do get an idea of flock sizes from Domesday Book, which commonly records the size of flocks as economic assets. As you might imagine, the size of flocks can vary wildly depending on the size of a settlement and the proclivities of the landowner. At Wimborne Minster in Dorset, for example, there were two separate flocks of 250 and 127 sheep respectively, while at Newton St Cyres just outside Exeter in Devon there were 400 sheep. The small village of Saltford outside Keynsham (near Bristol) also had a flock of arouns 120 sheep, while at Dewdon on Dartmoor there were 159 sheep.