One of the reasons the birch bark manuscripts were so important in re-evaluating the literacy rates of medieval Novgorod is because birch bark is not particularly valuable or durable, making it a poor trade good. Amongst other factors, that suggests that the use of birch bark was predominantly by the poor and lower middle class, who would ordinarily be expected to be illiterate.
https://www.ancient-origins.net/news-history-archaeology/birch-bark-letters-001806
One of the reasons the birch bark manuscripts were so important in re-evaluating the literacy rates of medieval Novgorod is because birch bark is not particularly valuable or durable, making it a poor trade good. Amongst other factors, that suggests that the use of birch bark was predominantly by the poor and lower middle class, who would ordinarily be expected to be illiterate.
Fascinating stuff!