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Wholesale Trade Survey: September 2009 quarter
Embargoed until 10:45am  –  07 December 2009
Technical notes

Background to the survey

The Wholesale Trade Survey (WTS) is designed to provide short-term economic indicators for the wholesale trade sector. In addition, the survey data is used to compile the wholesale trade sector component of quarterly national accounts.

The survey was last redesigned in the September 2002 quarter. For more detail about the redesign, refer to Wholesale Trade Survey – Redesign: September 2002, available on the Statistics New Zealand website. As a result of the redesign, a split between raw materials and finished goods stocks is now available. The analytical back series for each stock type has been calculated based on the ratio of raw materials to finished goods stocks collected in the September 2002 quarter.

Population

The target population for this survey is all kind-of-activity units (KAUs) operating in New Zealand that are classified as Wholesale Trade (Australian and New Zealand Standard Industrial Classification Division F) on Statistics NZ's Business Frame.

Sample design

The survey population is stratified according to:

  • industries defined by the ANZSIC-based ANZIND classification at the inter-industry level
  • size (in terms of the rolling mean employment number)
  • turnover (annualised GST sales).

Each ANZIND inter-industry classification contains between two and four substrata. Because of the contribution large units make to the economic activity within each industry group, they are all included in the sample. A portion of the remaining medium to large units is also included in the sample. In addition, small to medium-sized businesses have their data modelled from administrative data (GST and EMS) sourced from Inland Revenue. All wholesaling KAUs belonging to a selected 'enterprise' are included.

About 1,300 units have been selected from the entire population for the postal sample, and the data for approximately 13,500 units is modelled from tax data

Sample maintenance

Sample maintenance is the process that maintains the sample over time, to reflect births, deaths and other structural changes identified on the Business Frame. The information for Business Frame changes can be from a variety of sources, including GST registrations and respondent contact.

New enterprises are identified when they register for GST. Once a quarter, the new enterprises are selected into the sample using the same criteria as for the original sample. These are referred to as births. When an enterprise ceases trading, its wholesaling KAUs are removed from the survey. These are referred to as deaths.

Enterprises can also enter or leave the survey sample if they are reclassifications from another industry to wholesaling. Reclassifications occur when an enterprise changes its main form of activity (eg from manufacturing to wholesale trade). These are usually identified in the Annual Frame Update Survey (AFUS) conducted in February each year.

Sample reselection

The sample for the WTS is reselected each quarter to ensure that the sample reflects changes occurring in the wholesale trade population.

Measurement errors

Errors in the survey are divided into two classes:

Non-sampling error

Non-sampling error includes errors arising from biases in the patterns of response and non-response, inaccuracies in reporting by respondents, and errors in the recording and coding of data. The size of these errors is difficult to quantify. Data is subject to revision if significant errors are detected in subsequent quarters.

Sampling error

Sampling error is a measure of the variability that occurs by chance because a sample, rather than an entire population, is surveyed.

Industry descriptions

An activity unit is included in an industry based on its predominant activity in terms of operating income.

The 16 industries are defined as follows:

ANZSIC Class  
Unprocessed primary products  
Wool wholesaling 4511
Cereal grain wholesaling 4512
Farm produce and supplies wholesaling nec 4519
Petroleum product  
Petroleum product wholesaling 4521
Metal and mineral  
Metal and mineral wholesaling 4522
Chemical
Chemical wholesaling 4523
 
Builders' supplies  
Timber wholesaling 4531
Building supplies wholesaling nec 4539
Farm, construction machinery, and professional business equipment  
Farm and construction machinery wholesaling 4611
Professional equipment wholesaling 4612
Computer wholesaling 4613
Business machine wholesaling nec 4614
Electrical and electronic equipment  
Electrical and electronic equipment wholesaling nec 4615
Machinery and equipment nec
Machinery and equipment wholesaling nec 4619
Motor vehicle  
Car wholesaling 4621
Commercial vehicle wholesaling 4622
Motor vehicle new part dealing 4623
Motor vehicle dismantling and used part dealing 4624
Primary product food  
Meat wholesaling 4711
Poultry and smallgood wholesaling  4712
Dairy produce wholesaling 4713
Fish wholesaling 4714 
Fruit and vegetable wholesaling 4715
Food and grocery products
Confectionery and soft drink wholesaling 4716
Liquor wholesaling 4717
Tobacco product wholesaling 4718
Grocery wholesaling nec 4719
Textile, clothing and footwear
Textile product wholesaling 4721
Clothing wholesaling 4722
Footwear wholesaling 4723
Household good
Household appliance wholesaling 4731
Furniture wholesaling 4732
Floor covering wholesaling 4733
Household good wholesaling nec 4739
 
Wholesale trade nec
Photographic equipment wholesaling 4791
Jewellery and watch wholesaling 4792 
Toy and sporting good wholesaling 4793 
Wholesaling nec 4799 
Books and paper product
Book and magazine wholesaling 4794
Paper product wholesaling 4795
Pharmaceutical and toiletry
Pharmaceutical and toiletry wholesaling

4796

 

Definitions

ANZSIC

Australian and New Zealand Standard Industrial Classification system.

ANZIND

An ANZSIC-based classification used to group industries for publication.

Business Frame

A register of all economically significant businesses operating in New Zealand. The WTS population is drawn from the Business Frame.

Enterprise

A business entity operating in New Zealand either as a legally constituted body such as a company, partnership, trust, local or central government trading organisation, or as a self-employed individual.

Kind-of-activity unit (KAU)

A subdivision of an enterprise engaged in predominantly one activity and for which a single set of accounting records is available.

Rolling mean employment (RME)

RME is a 12-month moving average of the monthly employee count (EC) figure, which replaces the numbers of full-time and part-time employees.

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Operating income

Income from total sales. This includes:

  • sales of processed goods
  • sales of goods purchased for resale
  • sales of services
  • repair services
  • processing fees
  • management fees
  • rental income
  • leasing income
  • royalties
  • patent fees.

Operating income excludes:

  • interest/dividends received
  • donations
  • insurance claims
  • subsidies
  • government grants
  • exchange rate gains
  • extraordinary items
  • gains on sales of fixed assets
  • excise duties
  • bad debts.

Total stocks

Closing stocks of raw materials for use in production, plus the closing stocks of finished goods, work in progress and trading stocks.

Seasonally adjusted series

The X-12-ARIMA package has been used to produce the seasonally adjusted estimates and trend estimates for sales in all subdivisions. Seasonal adjustment aims to eliminate the impact of regular seasonal events (such as annual cycles in agricultural production, winter or annual holidays) on time series. This makes the data for adjacent quarters more comparable.

All seasonally adjusted figures are subject to revision each quarter. This enables the seasonal component to be better estimated and removed from the series.

Restructuring within the dairy industry has affected the primary product food industry series in the September 2002 quarter. In order to maintain the long-term continuity of the seasonally adjusted and trend series for primary product food and total wholesaling, the actual series is adjusted prior to the seasonal adjustment program being run. This adjustment to the actual series removes the discontinuity in the series.

The X-12-ARIMA seasonal adjustment package is very robust. However, problems occur when there has been an abrupt change in the seasonal variation, as with other seasonal adjustment packages.

Estimated trend

For any series, the survey estimates can be broken down into three components: trend, seasonal and irregular. While seasonally adjusted series have had the seasonal component removed, trend series have had both the seasonal and the irregular components removed. Trend estimates reveal the underlying direction of movement in a series, and are likely to indicate turning points more accurately than seasonally adjusted estimates.

The trend series are calculated using the X-12-ARIMA seasonal adjustment package. They are based on a five-term moving average of the seasonally adjusted series, with an adjustment for outlying values.

Trend estimates towards the end of the series incorporate new data as it becomes available and can, therefore, change as more observations are added to the series. Revisions can be particularly large if an observation is treated as an outlier in one quarter, but is found to be part of the underlying trend as further observations are added to the series. Typically, only the estimates for the most recent quarter will be subject to substantial revisions.

More information

For more information, follow the link from the technical notes of this release on the Statistics New Zealand website.

Copyright

Information obtained from Statistics NZ may be freely used, reproduced, or quoted unless otherwise specified. In all cases Statistics NZ must be acknowledged as the source.

Liability

While care has been used in processing, analysing and extracting information, Statistics NZ gives no warranty that the information supplied is free from error. Statistics NZ shall not be liable for any loss suffered through the use, directly or indirectly, of any information, product or service.

Timing

Timed statistical releases are delivered using postal and electronic services provided by third parties. Delivery of these releases may be delayed by circumstances outside the control of Statistics NZ. Statistics NZ accepts no responsibility for any such delays.

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