frtour1-8, Exercise 3: Testing the claim of billions of viewers

Model answer (check the details):

How to test it:
- Ask what is being counted: unique viewers, or viewer-hours, or "cumulative audience" (the sum of every viewer of every stage, counted again each time).
- Obtain the original data: ratings from the broadcasters in each country (the ratings agencies' figures), streaming and social media reports, and the organisers' own methodology note if one exists.
- Compare with independent estimates, such as those from sports business consultancies, and check the sums.
- Look at how the figure changes over time, and whether the method changed.

Difficulties:
- Cumulative figures count the same person many times (a viewer who watches 21 stages counts as 21), so a figure in billions does not mean billions of different people.
- Ratings systems differ from country to country, and some do not measure out-of-home or online viewing well.
- The organisers and broadcasters have an interest in large numbers, and the data are not always public.
- Roadside spectator counts are estimates, based on guesses by police and organisers.

Result: the claims are at best rough, and a careful writer reports them as the organisers' figures.

Care: no figure should be quoted without saying who produced it and how.