Adjusted parity index is a parity index that is symmetrical around 1 and limited to a range between 0 and 2.
Adjusted gender parity index (GPIA): If the female value of an indicator is less than or equal to the male value, the unadjusted and adjusted GPI are identical and calculated by dividing the female value of an indicator by the male value of the same indicator. If the female value is greater than the male value: adjusted GPI = 2 - 1 / (female value / male value). Adjusted location parity index (LPIA): If the rural value of an indicator is less than or equal to the urban value, the unadjusted and adjusted LPI are identical and calculated by dividing the rural value of an indicator by the urban value of the same indicator. If the rural value is greater than the urban value: adjusted LPI = 2 - 1 / (rural value / urban value). Adjusted wealth parity index (WPIA): If the poorest quintile value of an indicator is less than or equal to the richest quintile value, the unadjusted and adjusted WPI are identical and calculated by dividing the poorest quintile value of an indicator by the richest quintile value of the same indicator. If the poorest quintile value is greater than the richest quintile value: adjusted WPI = 2 - 1 / (poorest quintile value / richest quintile value).
Adjusted parity indices address certain disadvantages of the simple (unadjusted) parity indices: the latter are imperfect measures because they are not symmetrical around 1 and have no upper limit, with a theoretical range of 0 to infinity. For example, if the female primary net enrolment rate (NER) is 40% and the male NER is 50%, the gender parity index (GPI) has a value of 0.8. If the female and male values are reversed, the GPI has a value of 1.25, which gives the mistaken impression of greater gender disparity because 1.25 is at a greater distance from 1 than 0.8. With small indicator values, the unadjusted GPI can also take on very high values, far outside the usual 0 to 2 range.
GPIA: Female and male values of the given indicator. LPIA: Rural and urban values of the given indicator. WPIA: Poorest quintile value and richest quintile value of the given indicator.
An adjusted parity index equal to 1 indicates parity between the two compared categories. In general, a value less than 1 indicates disparity in favour of the category in the denominator (males for GPIA; urban for LPIA; richest quintile for WPIA) and a value greater than 1 indicates disparity in favour of the numerator category (females for GPIA; rural for LPIA; poorest quintile for WPIA). However, the interpretation is different for indicators that should ideally approach 0% (e.g. repetition rate, dropout rate, out-of-school rate, etc.). In these cases, a GPIA less than 1 indicates disparity in favour of females and a value greater than 1 indicates disparity in favour of males; an LPIA less than 1 indicates disparity in favour of those living in rural areas and a value greater than 1 indicates disparity in favour of those living in urban areas; and a WPIA less than 1 indicates disparity in favour of those living in the poorest households and a value greater than 1 indicates disparity in favour of those living in the richest households.