Labour Market Statistics: December 2019 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 the 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). This coincided with the Survey of Working Life (SoWL) supplement. A similar effect was seen the previous two times SoWL was run, in the March 2008 and December 2012 quarters. Adjustments were made to these two quarters using the X13 method, the seasonal adjustment software used at Stats NZ. This method involves looking at data before and after the quarter in question and determining, through modelling, a reasonable adjustment to the data.

The same data adjustment method could not be used in the December 2018 quarter, as the adjustment was made immediately and there was no ‘after’ data available. We used the adjustments from the March 2008 and December 2012 quarters to inform the interim adjustment to the December 2018 quarter.

This adjustment was run in addition to seasonal adjustment and was applied 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.

See DataInfo+ December 2018 quarter for more information about the original adjustment.

We have been reviewing the original data adjustment and the performance of X13’s adjustment for December 2018 quarter for five quarters. This quarter, we have concluded that there is enough ‘after’ data for the X13 method and new adjustments have been implemented. Additionally a minor update to the March 2008 and December 2012 quarters adjustments was made to account for revised population estimates.

###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 2019 quarter was 18.6 percent. This compares with 17.9 in the September 2019 quarter and 19.1 percent in the December 2018 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 June 2019 quarter unemployment rate was unchanged at 3.9 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