Labour Market Statistics: December 2018 quarter

#Period-specific information
##Response Rates

See New quality measures for the Household Labour Force Survey for more information on the sample rate and response rates.

##HLFS

###Adjustment to data series In the December 2018 quarter, Stats NZ observed a larger than expected number of people moving out of ‘employment’ to ‘not in the labour force’ (NILF). A similar effect was seen in previous quarters – the March 2008, March 2009, and December 2012 quarters. The March 2008, December 2012, and December 2018 quarters coincide with the Survey of Working Life (SoWL) supplement.

We made prior adjustments to the previous two quarters in which SoWL was run – the March 2008 and December 2012 quarters. These adjustments were implemented in the September 2013 quarter.

The seasonal adjustment package used by Stats NZ has an automatic procedure for dealing with outliers (observations which are far removed from the others in the series), which works well in most cases. However, in certain circumstances outliers need to be dealt with explicitly. This is done via a prior adjustment.

In the December 2018 quarter, we have made a prior adjustment, in addition to seasonal adjustment, to the following high-level data series to improve the accuracy of, and coherence between, the trend series and seasonally adjusted series:

• Male employed
• Female employed
• Male not in the labour force (NILF)
• Female not in the labour force (NILF)
• Full-time employed
• Part-time employed
• Employed 15 to 64 years
• NILF 15 to 64 years
• Usual hours worked
• Actual hours worked.

We used the adjustments from the March 2008 and December 2012 quarters to inform this adjustment. We will monitor these series over the next few quarters and may make future revisions.

Some seasonally adjusted employed and NILF series were not adjusted further this quarter. For example, the number of people employed, broken down by age; underemployment; and youth not in employment, education, and training series may show unrealistic movements this quarter. This data should be used with caution. In addition, all actual (unadjusted) employed and NILF series, including all age, ethnicity, industry, occupation, and regional breakdowns, should be used with caution.

Seasonally adjusting unadjusted data generated from the unit record files (Data Lab, IDI, and other unit-record files) will yield different results from those published because of Stats NZ’s seasonal adjustment settings and prior adjustments.

###Youth not in employment, education, or training We recommend caution when using the latest data on people aged 15–24 years who were not in employment, education, or training (NEET), and to focus on longer-term trends.

The distribution of our data collection throughout the December 2018 quarter affected the rise in NEET youth. More people than usual were surveyed towards the end of the quarter, when tertiary education had ended for the year. This means we were more likely to have captured youth who had ended their studies, and not yet started work or further study.

###Outliers During the seasonal adjustment process, X-13-ARIMA-SEATS can give less weight to the irregular component. Specifically, if the estimated irregular component at a point in time is sufficiently large compared with the standard deviation of the irregular component as a whole, then the irregular component at that point can be downweighted or removed completely and re-estimated. We refer to such observations as partial- and zero-outliers, respectively. In practice, the downweighting of outliers does little to seasonally adjusted data, but the impact of the outliers on the trend series will generally be reduced. However, if an outlier ceases to be an outlier as more data becomes available, then significant revisions to the trend series become possible.

There were no outliers in our main series in the last year.

###HLFS pre- and post-calibration weight The following figure shows that while the distribution of the pre- and post-calibration weights differs within a quarter, the difference between the weights typically does not change from quarter to quarter.

The undercoverage rate indicates how representative the pre-calibrated sample is. The higher the undercoverage rate, the less representative the pre-calibrated sample.

Usually the undercoverage rate in the HLFS is around 20 percent. The overall undercoverage rate for the HLFS in the December 2018 quarter was 20.2 percent. This compares with 18.6 in the September 2018 quarter and 18.9 percent in the December 2017 quarter.

###Revisions to HLFS

Each quarter, we apply the seasonal adjustment process to the latest quarter and all previous quarters. Every estimate is subject to revision each quarter as new data is added, which means that seasonally adjusted estimates for previous quarters may change slightly. In practice, estimates more than two years from the end-point will change little.

The September 2018 quarter unemployment rate was revised to 4.0 percent after we applied seasonal adjustment.

This table lists the changes in estimates between the current and previous quarters for the seasonally adjusted data.

This table presents revisions for the trend estimates. Trend revisions are generally larger than those of the seasonally adjusted data.

The table below shows the average of all such absolute revisions, expressed relatively, and indicates to what extent the current estimates might be revised when the revised data for the next quarter becomes available.

##General information and methodology

For general information and methodology on the specific surveys within the labour market statistics release, please see the following Datainfo+ pages:

• Household Labour Force Survey
• Labour Cost Index
• Quarterly Employment Survey