“…This has been identified in studies conducted in large geographical areas, such as in 35 European countries [26], Central Asia [30] as well as in 33 African countries [31], or in smaller studies comprising only one nation as, for example, Bulgaria [1,6,13,32,33], Poland [34,35], Hungary [2,[36][37][38][39][40], Greece [4,41], Lithuania [34,42], Russia [43,44]; Ukraine [34,45], Moldova [46], Serbia [47], Kazakhstan [48], Albania [5,49,50], Kosovo [8], Tajikistan [51,52], Kyrgyzstan [53], Taiwan [54], Cameroon [55], Tanzania [3,56] and Turkey [57]. Nevertheless, informal patient payments phenomenon is poorly examined at a cross-country level.…”