quote steve gardham, below
What I have always said is that approx. 90% of the canon of English traditional songs have their earliest extant version on printed street literature or similar. that's a FACT. My OPINION, after 50 years of studying the relationship between print and oral tradition and hundreds of individual songs, is that 95% of them originated in this way.

imo , an incorrect statement and a half truth, it appears to ignore any songs that were in existence before printing presses that were either composed by troubadours or court musicians or any other people.
my opinion is that traditional songs were composed and sung before the advent of printing presses, and that the present day trad repertoire is a mixture of both songs composed by broadside writers and by people who were not broadside writers,
there is evidence that indicates songs in Scotland were composed and known as botHy ballads, I find the idea that England was somehow different from ireland and scotland in that respect particularly as there was a lot of travel between the 3 countries an over simplistic argument.
Do you seriously think that fishermen travelling between the 3 countries and travelling farm workers who were english did not make up songs because they were English, whilst their Scottish and Irish counterparts did, IMO your line of argument is highly flawed .