4.3 Birthplace The existing literature shows that migrants face an elevated in-work poverty rate (Crettaz, 2018; Alvarez-Miranda, 2011). As our data comes from the 2013 Census rather than a survey, the latter of which is what most international analyses are based on, we can disaggregate the birthplace variable to a much greater degree than the binary migrant indicator often utilised in prior literature. To define the birthplace of a household unit, we classify a household based on the birthplace of each adult in the household. If, for example, there are two adults in the household unit, both born in the same country, they will be counted as one household unit associated with that particular birthplace. If the two adults in the household are born in different countries, then they are counted as a household unit with each of those respective birthplaces. Therefore, the number of working household units by birthplace (865,161) is larger than the initial sample (725,313). The in-work poverty rate of this larger sample, where household units are defined by birthplace, is 6.9 percent. The in-work poverty rates for different birthplaces, relative to the sample average, are illustrated in Table 5. First, we note that households with at least one adult born in New Zealand face the average in-work poverty rate. With respect to migrants, there is substantial heterogeneity regarding in-work poverty experience based on birthplace location. For example, migrants from Polynesia (+2.3 percentage points) or North-East Asia (+7.4 percentage points) experience a substantially higher in-work poverty rate. In contrast, migrants from the United Kingdom (-1.7 percentage points), Maritime South-East Asia (-1.1 percentage points) or Southern and East Africa (-2.1 percentage points) have a below-average in-work poverty rate. It is necessary to view the in-work poverty results in Table 6 in conjunction with the share of total household units to gauge the size of the affected population. For instance, Table 6 illustrates that two out of three households have at least one adult member who is born in New Zealand; about 9 percent of households have an adult born in the United Kingdom; and 5 percent are associated with a Polynesian birthplace. Furthermore, for households where one adult was born in Central Asia or Micronesia, their respective in-work poverty rates are 16.1 and 11.2 percentage points higher than the sample average; however, each of these birthplace sub-groups only accounts for 0.1 percent of the total sample. This means that caution should be taken when interpreting the results relating to groups with a very small representation in New Zealand, as the sub-sample size may be too small to provide statistically valid estimates. Page 26