How have historians traditionally answered this question and how is Marsh’s answer different?

What were broadsheet ballads?- Marsh based his study on the best-selling ballads of the seventeenth century, accusing previous historians of unsystematically picking and choosing from surviving ballads. In the absence of sales figures, how did he identify which ballads were the most popular ones?- Marsh’s central research question is “How were husbands and wives represented in hit songs of the 17th century?” and he spends the bulk of his lecture answering it. How have historians traditionally answered this question and how is Marsh’s answer different?This is the link for the video https://vimeo.com/245277663