Data Sources and Definitions

Data for most dimensions of the “What’s My GPG” tool is taken from the 2019 Household Labour Force Survey, a sample survey of approximately 30,000 respondents which collects income information annually.

All statistical breakdowns are subject to sample error, including the national gender pay gap as reported by Stats NZ. Sample errors increase as further breakdowns are made, for example the gender pay gap between workers aged 15 to 19 is calculated using a very small source group. In selecting data for “What’s My GPG” the Ministry for Women has considered long-term trends to ensure any pay gaps reported are real, and have continued to manifest over time.

The gender pay gap for most dimensions is calculated between groups as the difference between median hourly earnings. There is no standard measure of pay differences, and users may encounter other comparisons, such as those using averages (means) rather than medians. No matter how data is analysed, pay gaps between men and women exist and persist.

The Ministry for Women considers that by examining pay gaps by different populations, New Zealanders can best consider different solutions to reducing pay gaps for everyone.

As noted, pay gaps for fields of study have been calculated using the difference in median annual income, and are therefore not directly comparable to pay gaps reported for other dimensions. Source data for the field of study report was derived from the Integrated Data Infrastructure (IDI), and provided by the Tertiary Education Commission.

IDI data is not subject to sample error in the same way as survey data, however it does suffer from some attrition where admin data sources cannot be matched. ‘False positives’ may appear when probabilistic matching incorrectly combines some records.

For more information on pay differences by qualification and detailed commentary, refer to earlier reports published by the Ministry of Education.