Page 148 - Special Topic Session (STS) - Volume 4

STS571 Ossi Nurmi et al.
The following example presents an imaginary case of the roaming events
and outbound trips deduced for a single subscriber during a 30 days period.
This subscriber is a particularly active traveller and five outbound trips are
registered during the 30 days period.
Day
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
Roaming events
Trips
Country 1 1. 5.
Country 2 2.
Country 3 3. 4.

Day trip
Short trip (1-3 nights)
Long trip (over 3 nights)

Figure 1 - Roaming events and outbound trips of a subscriber

Roaming events are registered whenever the subscriber is making calls,
sending sms or using data in a mobile network abroad. The first event in a
country indicates the beginning of the trip to that particular country. A total
of five outbound trips were registered for this subscriber.

3. Methodology for estimating outbound trips
The target population consists of all outbound tourism trips made by
Finnish residents. The reference data is collected by Statistics Finland’s Finnish
Travel –survey with a sample size of 28,200 persons out of which 14,700 were
interviewed by phone concerning trips that ended during 2017. The data
provided by the Finnish MNOs should be treated as samples of all outbound
trips made by Finnish residents in 2017. Two out of three operators have
provided the data and the market share of each operator is roughly one third
of all subscribers. The source data thus contains the outbound trips of two
thirds of the Finnish residents and one third are missing. As with every sample,
the MNO data is of limited use by itself and coefficient weights are needed to
estimate the target population: all outbound tourism trips. According to the
Finnish Travel –survey, Finnish residents made 10.5 million outbound trips in
2017. This is annually a relatively stable figure based on 2,700 trips reported
by the respondents. In order to avoid many of the known pitfalls related to
over- or underestimation in MNO data, this annual figure of 10.5 million
outbound trips, is used as a frame and MNO data is first simply weighted using
the following formula:

ℎ =
∑( )

This simple weight coefficient is thus obtained by dividing the annual
outbound tourism trips by sum of trips made by the subscribers of each MNO.

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