“…Levels and characteristics of socioeconomic inequality differ between studies, depending on the data used. Some authors relied on individual socioeconomic or socio-demographic characteristics alone [ 26 , 29 , 31 , 37 , 38 , 44 , 47 , 50 , 52 , 54 , 55 , 58 ], such as maternal education level [ 26 , 31 , 32 , 33 , 34 , 35 , 37 , 38 , 39 , 42 , 43 , 44 , 45 , 47 , 48 , 50 , 52 , 54 , 55 , 56 , 57 , 58 ], paternal education level [ 34 , 38 , 52 ], employment [ 37 , 55 , 58 ], income [ 26 , 38 , 46 ], etc. Others used neighborhood socioeconomic characteristics only [ 28 , 30 , 51 , 53 ], such as neighborhood income index [ 28 , 30 , 32 , 35 ,…”