In Croatia, Duper families are generally Croats (from Dubrovnik area ), very rarely Serbs. In the past century, relatively most of Croatian residents bearing this family name were born in Dubrovnik and Daruvar.
Prevalence
About 40 people with faimily name Duper live in Croatia today, in 20 households. There were 70 of them in the middle of the past century, and their number decreased by 40 percent. They are located in 7 Croatian counties, in 7 cities and threee other places, mostly in Mlini in Dubrovnik area (40), Dubrovnik (<10), Daruvar (<5), Pula (<5), and in Mokosica (<5).
In the sources analysed in the project Acta Croatica so far, the name is mentioned few times, the first time 1930 in source Emigration Commission Zagreb.