Here are the data for Germany:I only found the charts from 1960 on:
- Number one folksong in the charts for the 1960s was 'Oh my darling Clementine' which topped the charts for many weeks and was overall No. 2 in 1965 (which was a good year for folk also seeing 'If I had a hammer' in the overall top 10
- also in the top 10 (over the whole year) or at least once No. 1 were La Paloma (1961; old German lyrics), Hohe Tannen (1960), Heidschi Bumbeidschi (1969), Aloahe (1962; new German lyrics, Hawaiian tune), and several others (sometimes only the tune trad.)
- I didn't check all the 70s, but 1970 is hard to beat for folk: overall No. 1 and many weeks in sucession No. 1: El condor pasa, a close No. 2 and many weeks No. 1 'House of the rising sun'
- a special year was 1974, when German president Walter Scheel came in the charts for several weeks in succession with No. 5 being the best position singing the folksong 'Hoch auf dem gelben Wagen'.
Wolfgang