Introduction of mobile phone interviewing to the national visitor survey



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FACT SHEET

introduction of MOBILE PHONE INTERVIEWING to the NATIONAL VISITOR SURVEY

Background


The National Visitor Survey (NVS) commenced in 1998. Between 1998 and 2013, all interviews were undertaken with respondents on residential fixed-line telephones using Computer Assisted Telephone Interviewing (CATI).

The mobile only population has increased substantially in recent years particularly for younger age groups. Latest estimates indicate that 30% of those aged 15-24 years and 47% of those aged 25-34 years are mobile only.

Given this, to provide better coverage of the Australian population, Tourism Research Australia (TRA) has introduced mobile phone interviewing as of 2 January 2014. This has seen a break in series because the travel patterns of people interviewed on mobile phones differ from those of people interviewed on residential fixed-lines and these cannot be back-cast reliably by estimation.

HOW DOES THE NEW METHODOLOGY WORK?


The NVS continues to have an annual sample of 120,000. For 2014, this is split evenly between fixed-line (50%) and mobile phone (50%) sample, resulting in three phone ownership populations:

  • Fixed-line only (reached through the fixed-line sample)

  • Mobile phone only (reached through the mobile phone sample)

  • Fixed-line plus mobile phone (reached through either sample segments).

The NVS weighting process has been modified to account for coverage of persons with fixed-lines and/or mobile phones. For further information on the weighting regime used under the new NVS methodology refer to (link to be added).

The same information is collected from those interviewed on fixed-lines and mobile phones. However, some additional screening questions are included for mobile phone respondents to ensure it is safe for them to be interviewed.


HOW HAS THE NVS SAMPLE PROFILE CHANGED?


The introduction of mobile phone interviewing provides a sample distribution by age that aligns more closely with that of the Australian population aged 15 years or more. Previously, there was considerable under-coverage of those aged 15-34 years (more likely to be mobile only) and over-coverage of people aged 55 years and over (more likely to live in fixed-line households) (Table 1).

Overall, those interviewed on mobile phones are:

More likely to be aged 15 to 34 years (41% compared with 10%) and less likely to be aged 65 years or more (10% compared with 40%) than those interviewed on fixed-lines.

More likely to be employed full-time (47% compared with 30%).and less likely to be retired (14% compared with 43%) than those interviewed on fixed-lines.



More likely to be male (53% compared with 43%) than those interviewed on fixed-lines.

Table 1: NVS sample profile by age, March quarter 2013 and 2014

Age group

NVS March quarter 2013

NVS March quarter 2014

Population




Sample

%

Sample

%

%

15-24

2,146

7.4

3,615

12.2

16.8

25-34

2,037

7.0

3,991

13.4

18.0

35-44

4,293

14.8

4,236

14.2

17.1

45-54

5,152

17.7

4,997

16.8

16.4

55-64

6,097

21.0

5,479

18.4

14.0

65 or more

9,354

32.2

7,427

25.0

17.6

Total

29,079

100.0

29,745

100.0

100.0

The distribution of NVS sample across origin areas has also changed with the introduction of mobile phone interviewing. While pre-existing quotas for fixed-line sample have been halved for the 13 origin stratum (a), geographic quotas cannot be applied to mobile phone sample at this time. Instead, the mobile phone sample falls out randomly with some origin stratum receiving more and others less sample than in the past. A review into whether the change in distribution of sample by origin area has any impact on survey estimates is underway.

HOW iS tra quantifying the impact OF MOBILE PHONE INTERVIEWING on survey estimates?


The NVS estimates that TRA is publishing from March quarter 2014 onwards are based on the new methodology (i.e. compiled using survey responses from the fixed-line plus mobile phone sample). However, TRA has also derived some top-line fixed-line only estimates for comparison purposes.

While the fixed-line only estimates are constructed from half the sample collected previously and thus are subject to higher sample error, they provide a useful indicator of what the NVS estimates would have been had mobile phone interviewing not been introduced. Given this, the difference between the estimates published by TRA in 2014 and the fixed line only sample estimates help to quantify the impact from introducing mobile phone interviewing.


how much can be learnt from march quarter 2014 results?


Quarterly NVS survey estimates are subject to greater sample error than rolling annual (year ending) NVS survey estimates. Given this, March quarter 2014 survey results should be regarded as providing only a useful early indicator of likely broad impacts from introduction of mobile phone interviewing. A clear picture of the extent to which NVS survey estimates are impacted and how this effect varies for key national, state and regional tourism metrics will take some time (at least a year) to be known.

broad impacts evident for march quarter 2014

key tourism metrics


With the demographic profile of those interviewed on mobile phones and fixed-lines dissimilar, it is not surprising that March quarter 2014 data indicate that the travel patterns of those interviewed on mobile phones and fixed-lines are different.

People interviewed on mobile phones reported more overnight trips than those interviewed on fixed-lines.

Overnight trips taken by people interviewed on mobile phones were on average shorter than those of people interviewed on fixed-lines.

(a) The NVS has origin stratum: Sydney, Other New South Wales, Melbourne, Other Victoria, Brisbane, Other Queensland, Adelaide, Other South Australia, Perth, Other Western Australia, Tasmania, Northern Territory and Australian Capital Territory.

With trip length shorter, overnight expenditure per trip was lower but expenditure per night nonetheless higher for people interviewed on mobile phones than fixed-lines.

People interviewed on mobile phones reported more day trips than those interviewed on fixed-lines but similar average expenditure per trip.

People interviewed on mobile phones were almost twice as likely to report an outbound trip as those interviewed on fixed-lines.

Table 2: Key tourism metrics, March quarter 2014

Metric

Fixed-line only

Published

Difference (%)

Overnight trips (million)

20.1

21.6

7

Visitor nights (million)

87.8

87.3

-1

Overnight trip expenditure ($ billion)

14.01

14.19

1

Average nights (number)

4.4

4.0

-7

Average expenditure per trip ($)

696

658

-6

Average expenditure per night ($)


159

162

2

Day trips (million)

39.7

41.6

5

Day trip expenditure ($ billion)

3.96

4.21

6

Average expenditure per trip ($)

100

101

1

overnight travel patterns


In relation to domestic overnight travel, March quarter 2014 data highlight a number of differences in travel characteristics between those interviewed on mobile phones and fixed-lines. These include:

Landline only respondents (13%), previously over-represented in the NVS sample, were much less likely to report an overnight trip than mobile only (26%) or mobile plus fixed-line respondents (29%).

People aged 15-34 years who were interviewed on mobile phones reported significantly more overnight trips than those interviewed on fixed-lines.

Those aged 65 years and over who were interviewed on mobile phones also reported more overnight trips than those interviewed on fixed lines.

Overnight trips to visit friends and/or relatives (VFR) and for business were more likely to be reported by people interviewed on mobile phones than fixed-lines.

Intrastate trips were more likely to be reported by people interviewed on mobile phones than fixed-lines.



People interviewed on mobile phones participated in a higher number of activities on their trip than those interviewed on fixed-lines.

Table 3: Overnight travel by age, March quarter 2014

Travel characteristic

Fixed-line only

Published

Difference (%)

Age group (million)










15-34

5.9

7.2

23

35-64

11.6

11.4

-1

65+

2.7

3.0

9

Purpose of visit (million)










Holiday

9.8

9.8

0

VFR

6.4

7.6

20

Business

3.2

3.6

12

fly-in fly-out (fifo) travel


The NVS has always reported some FIFO travel but this has been under-estimated for two reasons:

  • The FIFO population is very mobile and thus not easily reached on residential fixed-lines.

  • An indeterminable number of FIFO trips were previously classified as out-of-scope by NVS interviewers because they involved travel between two places of usual residence.

Given the potential for FIFO travel to crowd out leisure travel in many parts of Australia, TRA has included three new questions on the NVS in 2014 to better identify FIFO workers and distinguish between their work and non-work related travel. While it will take more time to assess how effective these questions have been, data for March quarter 2014 indicate an increase in FIFO travel with the majority reported by people interviewed on mobile phones.

is there an impact on year ending march 2014 survey estimates


There is an impact on year ending March 2014 survey estimates from the introduction of mobile phone interviewing but this is diluted by the presence of data for the June, September and December 2013 quarters collected from fixed-line interviews only. The impact on year ending estimates will build as June, September and December quarter 2014 data progressively replace data for the same quarters in 2013. Year ending December 2014 survey estimates will provide the first annual data where the impact of mobile phone interviewing is fully integrated.

has mobile phone interviewing IMPROVED THE accuracy OF SURVEY ESTIMATES


The introduction of mobile phone interviewing has improved the age and gender distribution of the NVS sample. This has contributed to a more evenly distributed spread of weights being applied to the sample than before. For further information on the weighting regime used under the new NVS methodology refer to (link to be added).

The March quarter 2014 data indicates that the new methodology has reduced the relative standard errors (RSEs) of NVS estimates and this is expected to contribute to an improvement in survey accuracy and stability. TRA will be recalculating and publishing the RSEs attached to different sized NVS estimates collected under the new survey methodology in conjunction with its December 2014 NVS release.


comparing 2014 survey estimates with those for previous years?


As indicated previously, the introduction of mobile phone interviewing has seen a break in series because the travel patterns of people interviewed on mobile phones differ from those of people interviewed on fixed-lines. Given this, care should be taken when comparing March quarter 2014 and year ending March 2014 survey estimates with data from previous years.

The March quarter 2014 survey results indicate that data for earlier periods is likely to have under-estimated domestic overnight travel for younger visitors and the purpose of VFR and business. This is of particular relevance to the period 2008 to 2013 when growth in mobile phone ownership in Australia was particularly strong.


will tra be continuing to assesS the impact of mobile phone interviewing on the nvs


TRA will continue to analyse the impact of mobile phone interviewing as data for June, September and December quarter 2014 are processed. This fact sheet will be updated with each release to communicate what TRA learns as more data is collected and processed under the new methodology.

By the December 2014 NVS release TRA expects to have a much clearer picture of the extent of the impact and how this varies across a broad range of data items. This information will be shared with users of NVS data. While this will not eliminate the break in series, the information should assist in enabling informed and appropriate comparison of NVS data collected under the current and previous survey methodology.


is further change to the nvs sample methodology likely?


TRA monitoring of phone ownership patterns will be on-going. With mobile phone ownership continuing to grow and the number of fixed-line only households contracting quite quickly it is likely that there will be increases to the current 50% share of sample interviewed on mobile phones in future years. Pending the outcome of the review currently underway, it is also possible that steps may be taken to adjust the distribution of NVS sample by origin area at some time in the future.

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