In Croatia, Dupljak families are predominantly Croats (from Vinkovci area ), rarely Bosniaks (from Kosovo ), and very rarely Serbs. In the past century, relatively most of Croatian residents bearing this family name were born in Kosovo and in Karlovac.
Prevalence
About 20 people with faimily name Dupljak live in Croatia today, in 7 households. They are located in only five naselja i to in Osijek (<10), Visnjevac (<10), Karlovac (<5), Bijelo Brdo in Vinkovci area (<5), and in Pula (<5).
Outside Croatia
Family name Dupljak (including: Duplyak , Dupliak ) is present in 17 countries on three continents. The family name "Dupljak " is used by small number of people in the United States.