BARB, the organisation that reports television viewing figures in the United Kingdom, has published a list of the most popular programmes of 2017 as measured across personal computer, table and mobile screens. The numbers, in television terms, are surprisingly small.

In 2017, the most popular on-demand programme across personal computer, tablet and mobile screens, as reported by BARB, was the BBC series Three Girls, a worthy and gritty three-part drama, which had 611,000 average programme streams for its first episode. This was followed by the dating show Love Island from ITV, with 541,000 streams. The first episode of the nature documentary series Blue Planet II ranked sixth, with 383,000.

Love Island was the most popular programme viewed live on these platforms, with 249,000 average programme streams. The next most popular was I’m a Celebrity – Get me out of here! with 182,000, ahead of Election 2017 from the BBC, with 158,000. The most popular sporting event was a Premier League football match between rivals Liverpool and Everton on Sky Go, with 122,000, ranking fifth.

These numbers do not currently include viewing on television screens, which is a significant omission. However, they count viewing in the same way as television programme ratings, and are duration-based measuring the average number of streams over the course of the programme.

Average programme streams is an industry- metric that indicates the popularity of an online television programme. It’s the total viewing time of a programme on a TV Player by all devices in the reported period, divided by the full length of the programme.

It is comparable to the average audience measure typically used to report television programme audiences, although technically it is a measure of device usage, rather than the number of people viewing.

The metric has been ratified by JICWEBS, the industry body responsible for the development of standards in measuring online media performance.

Nonetheless, they do not seem to be very large numbers.

Compare these numbers with those reported by the BBC for its iPlayer service. The BBC said that the most requested programme of 2017 was the first episode of Blue Planet II with 4,768,000 requests. The drama Three Girls ranked fourth, according to the BBC, with 3,588,000 requests.

The BBC reports that computer, tablet and mobile requests accounted for 51% of iPlayer requests at the start of 2017, falling to 46% at the end of the year.

Even if the BARB figures only include half of the online viewing, there is still a considerable difference between the BBC claim of 3,588,000 requests for an episode of Blue Planet and the BARB report of just 383,000 average streams for the same episode.

The same episode of Blue Planet had a seven-day television audience of 14.01 million, as reported by BARB, rising to 14.88 million over 28 days, making the most viewed programme in the United Kingdom of 2017.

If we take the BARB figures, total online viewing on computer, mobile and tablets was equivalent to about 2.6% of the television audience. Yet according to the BBC figures, the total iPlayer requests look more like 24%.

How do we reconcile these figures? No doubt BARB will be in contact to shed some light on this, but it seems that the BARB TV Player Report has a very different view of online consumption in terms in television rating terms to the number of requests reported by the BBC in its Performance Report.

BARB says its TV Player Report is the UK’s only fully-audited, joint industry measure of online TV viewing on personal computers, tablets and smartphones. Online viewing data is generated by software code that has been added to 40 different online platforms, as audited by ABC.

Whenever someone in the UK watches a programme through a TV player app, either live or on-demand, the embedded software creates viewing statements detailing what has been watched, and, to the second, for how long. This census-based information is collected by Kantar Media and represents total viewing levels for participating online platforms on these devices.

For its part, the BBC says it counts the number of successful requests to stream or download a programme. Where programmes are downloaded for later viewing, where possible it reports playback rather than downloads. So why the big differences in numbers?

In theory, online viewing should be ultimately measurable and reportable, based on requests received and responses delivered. Achieving this is rather more complicated.

BARB is looking to provide a ‘gold standard’ of online viewing, similar to the common currency used to trade commercial television advertising. Achieving this is even more complicated.

Yet what is seems to show is that, online viewing, at least through computers, tablets and phones, amounts to a relatively small proportion of the audience to even the most popular programmes when measured in television terms.

The Viewing Report is available from BARB. The BBC iPlayer Performance Report is published by the BBC.