“…Multiple behavioral concepts were tested in the identified studies, but the majority involved social norms [ 44 – 46 , 48 – 50 , 54 , 56 , 57 , 59 , 62 – 64 , 69 , 77 , 81 ] ( n = 16), defaults [ 42 , 43 , 47 , 50 , 51 , 53 , 55 – 58 , 65 , 68 , 82 ] ( n = 13), availability [ 44 , 45 , 50 , 52 , 60 , 71 , 72 , 75 ] ( n = 8), framing [ 44 , 47 , 56 , 61 ] ( n = 4), loss aversion [ 76 , 79 , 80 ] ( n = 3), and present bias [ 76 , 79 ] ( n = 1). A variety of study designs was observed among all studies, but most were randomized controlled trials [ 44 , 46 , 47 , 49 , 50 , 54 , 59 , 60 , 63 – 65 , 67 – 70 , 73 – 76 , 78 – 85 ] ( n = 27).…”