National Visitor Survey methodology
Since 1 January 2005, interviews have been conducted with approximately 120,000 Australian residents aged 15 years and over on an annual basis. Prior to 2005, the sample size was 80,000, with the increase designed to enhance estimates for smaller states/territories and at a regional level.
Respondents are interviewed in their homes using random digit dialling and a Computer Assisted Telephone Interviewing system. The survey contains over 70 questions regarding:
 Destination
 Purpose
 Transportation
 Travel package
 Sources to obtain information about the trip
 Activities
 Expenditure
 Accommodation
 Travel party
 Demographics.
NVS definitions are based on those provided by the United Nations World Tourism Organization and therefore interviews are conducted with people who have travelled for purposes including holiday, visiting friends and relatives, business, education and employment. These travellers must not have been away from home continuously for more than 364 days, or in a leap year 365 days.
The NVS has been designed to optimise the reliability of regional estimates. Respondents interviewed in the NVS are randomly sampled to be representative of the Australian population, based on place of residence, age and sex.
The NVS is funded by the Commonwealth, state and territory governments under the auspices of the Australian Standing Committee on Tourism (ASCOT).
Results from the NVS are published quarterly and are available for free from the Tourism Research Australia website, go to http://tra.gov.au/research/latestnvsreport.html
Break in series between NVS and DTM
The previous major source of domestic tourism data, the Domestic Tourism Monitor (DTM), was conducted by the Bureau of Tourism Research (BTR) until March 1998. The NVS was introduced in January 1998 replacing the DTM. The NVS not only provides more information than the DTM on the characteristics and travel behaviour of Australians who travel within Australia, but also collects information on leisure activities, expenditure and outbound travel, which was not available from the DTM.
Aspects of the sampling and collection methodologies and the NVS questions themselves are quite different from those used in the DTM. Because of these differences, the results from the NVS cannot be compared with those from the DTM and differences between the results from the two surveys cannot validly be interpreted as changes in the level of tourism activity or travel behaviour of Australians.
Weighting and benchmarking
Weights for the NVS are calculated on an individual trip basis. They take into account the age, sex and place of origin of the respondent, the size of the household in which they live, month of travel, the recall period applicable to the trip (for example, 7 days for day trips, 28 days for overnight trips and 3 months for overseas trips) and the number of interviews with a return date in this recall period. The NVS is benchmarked to population estimates of those aged 15 years and over.
Determining domestic visitor expenditure in regional Australia
The NVS provides information on travel activity and expenditure by domestic visitors. Information on expenditure by these visitors is only collected for the respondent’s entire journey, not for individual stops. In order to determine the impact that the visitor activity is having on a particular region, Tourism Research Australia uses a model based approach to allocate visitors’ expenditure to Australia’s tourism regions.
Data reliability
Reliability of NVS data
The results given in the NVS are based on a sample, rather than a census, of Australian residents. As with all sample surveys, the results are subject to sampling variability and therefore may differ from figures that would have been obtained if the entire Australian population had been included in the survey.
A measure of the possible degree of difference is given by the confidence interval, which indicates the extent to which an estimate might vary by chance from the true figure because only a sample of the population was included.
In Table A, the 95% confidence interval widths are given for a range of estimates available in the NVS. These confidence intervals are expressed as a percentage of the estimate. That is, there are approximately 19 chances in 20 that the true figure (which might be obtained from a census) is within the range identified by applying the figures in the table.
Table A Confidence intervals for NVS estimates at the 95% level
Estimate ('000)

Overnight visitors

Visitor nights

Overnight expenditure

Day visitors

Day visitor expenditure

Overseas trips

20

>50

>100

>100

>100

>100

37.5

50

47.5

>100

>100

>50

>100

23.3

80

37.7

>100

>100

>50

>100

18.3

100

33.8

>100

>100

>50

>100

16.3

200

24.0

>50

>100

42.2

>100

11.3

300

19.6

>50

>100

34.6

>100

9.2

500

15.3

45.7

>100

26.9

>100

7.1

1 000

10.8

32.4

>100

19.1

>100

4.9

2 000

7.7

23.0

>100

13.5

>100

3.4

3 000

6.3

18.8

>100

11.1

>100

2.8

5 000

4.9

14.6

>100

8.6

>100

2.1

7 000

4.2

12.3

>100

7.3

>100

1.8

10 000

3.5

10.3

>100

6.1

>50


20 000

2.5

7.3

>50

4.3

>50


30 000

2.0

6.0

>50

3.6

>50


50 000

1.6

4.6

>50

2.8

45.8


70 000

1.3

3.9

49.5

2.3

39.8


100 000

1.1

3.3

41.8

2.0

34.2


140 000

0.9

2.8

35.7

1.7

29.7


200 000

0.8

2.3

30.1

1.4

25.5


500 000

0.5

1.5

19.5

0.9

17.3


1 000 000


1.0

14.1


12.9


2 000 000



10.1


9.6


5 000 000



6.6


6.5


10 000 000



4.7


4.9


20 000 000



3.4


3.6


50 000 000



2.2


2.5


In Table A, the areas above the lines indicate estimates which have large confidence intervals (greater than 100% of the estimate above the solid line and between 50% and 100% of the estimate in the area between the dotted and solid lines). These estimates are subject to sampling variability which is too high for practical purposes and should be used with caution in analysis or in the reporting of NVS estimates, as they have a large margin of error. The area below the dotted line contains estimates with smaller confidence intervals. That is, the estimates are closer to the values that would be obtained if the entire Australian population were interviewed.
The following example illustrates the use of the table to determine 95% confidence intervals for NVS estimates.
The estimated number of overnight visitors to a particular state was 7,000,000. Looking at the ‘Overnight visitors’ column this estimate has a 95% confidence interval of plus or minus 4.2%. Therefore, there are 19 chances in 20 that, if the entire population had been included in the survey, we would obtain a figure which is within the range 7,000,000 plus or minus 4.2% of this estimate, that is, in the range 6,706,000 to 7,294,000.
For users who are familiar with statistical estimation techniques and the use of standard errors, the values in the above table are derived from the following linear regression equation:
LN (RSE) = A + B*LN(ESTIMATE)
where RSE is the relative standard error and the model parameters are:
In the above example of overnight visitors to a particular state:
LN (RSE) 
= 0.512561685+ 0.493277162*LN(7000) 

= 3.85475 
RSE 
= EXP (3.85475) 

= 0.021 

= 2.1% 
The 95% confidence interval is then found by multiplying the RSE by 1.96 
95%CI 
= +/ 4.2% 
Although confidence intervals are useful in indicating the reliability of one data item, they cannot simply be added to detect whether movements in data items between two periods of time are statistically significant. The following formula gives an approximation of the confidence interval width for the difference between two estimates:
SQUARE ROOT(2) * CONFIDENCE INTERVAL WIDTH
Note that this formula is an approximation only and assumes that the two estimates being tested are of similar size and are based on similar samples.
In the example used above, an observed change from our estimate of overnight visitors of 7,000,000 would be significant (at the 95% level), if there is a difference in a subsequent or earlier estimate of 5.9% (1.4142*4.2%) or more. Therefore, if another estimate is outside the range 6,587,000 to 7,413,000 (+/ 5.9%), we can state that there are 19 chances out of 20 that the apparent movement reflects a true trend in the population.
Use of NVS data to analyse National, state/territory, or regional domestic tourism performance should be based on an understanding of the data’s level of reliability. Through understanding the confidence interval of the data, users are able to determine when a change between years is likely to be statistically significant and when it is not (that is, when it is more likely to be simply the result of random sample variation).
Items that are not collected for long trips
In the NVS, information on purpose, accommodation, transport, leisure activities and detailed expenditure items are not asked for at individual locations visited on long trips. A long trip is defined as one where a person stops overnight in more than 21 different locations.
Indications of reliability in data tables
All figures reported in this publication are estimates based on the sample surveyed and as such are subject to some degree of uncertainty, indicated by the size of the confidence interval associated with the estimate. Estimates that have a confidence interval width between 50% and 100% are marked with a single asterisk (*) in tables. When the confidence interval width exceeds the estimate (that is, is greater than 100%), the estimate is marked with a double asterisk (**).
Where the estimate is marked with either a * or ** symbol, the estimate is subject to sampling variability which is too high for most practical purposes.
Use of symbols in tables
na data not available
* subject to sampling variability too high for practical purposes (confidence interval width between 50% and 100%)
** subject to sampling variability too high for practical purposes (confidence interval width of 100% or more)
Row and column totals
Items within the body of each table may not add exactly to row or column totals. This is due to rounding and to inclusion in totals of unallocated ‘not stated’ or ‘unspecified’ responses.
In some tables, the row or column total may be considerably different to the sum of the component values. This occurs due to multiple responses to some questions in the NVS questionnaire. Where items within the body of a table do not add exactly to row or column totals, a footnote has been provided.
State and territory specific surveys
The Tasmanian Government conducts a regular survey of visitors to the state. Results of the survey are available from Tourism Tasmania:
Tourism Tasmania
GPO Box 399
Hobart TAS 7001
Phone: (03) 6230 8231
Fax: (03) 6230 8353
Email: statistics@tourism.tas.gov.au
Web site: www.tourismtasmania.com.au
Image: Cape Range National Park. Courtesy of Australia's Coral Coast/Tourism Australia.