BARB Explained: Why duration-based metrics are important 29 May 2018 We recently conducted a consultation to explore the expectations that advertisers and agencies have for a cross-platform audience currency; it’s clear that the industry views duration-based metrics as fundamental to audience measurement. But why are they so important? The chief alternative to duration-based metrics is the reach measurement. Reach is the net number or percentage of people who have seen a specified amount of a particular piece of content; for television, this might be a programme, channel or advertising campaign. The amount of viewing that an individual must have done in order to be counted as having been reached varies by medium. The BARB definition is for this to be at least three consecutive minutes. This means that the reach figure for a television programme is often much higher than the average audience figure, but arguably less meaningful. Reach provides an indication of the number of people that watched at least three minutes of a show – but they may have not liked the show and so switched off, or they may have just caught three minutes of the middle of a programme while channel-surfing. By contrast, average audience represents the total amount of time viewed, which is a more reliable indicator of popularity; after all, if you enjoy a show you are likely to watch more of it. We can see a number of examples of this if we look at the reach compared to the average audience for various recent programmes in the table below. *ITV Weather reach based on 1 minute of continuous viewing due to programme length It is logical that average audience figures are considerably different to reach figures for certain programmes. For instance, viewers may tune into Eurovision simply to judge the UK entry or to catch the results. By contrast, those that watch a soap, like Coronation Street, are committed fans engaged by the narrative and so are likely to watch the whole broadcast. The ITV Weather has a high reach thanks to inheriting an audience from the news, but a lower average audience, perhaps because viewers start switching off when they remember that forecasts are unreliable! Why the average audience for The Graham Norton Show is so much lower than the reach is a little harder to unpick, but given that 34% of viewing to this episode was timeshifted, it may be that viewers were fast-forwarding though the show to get to their favourite guest, be it David Beckham, Ryan Reynolds or BAFTA winner Vanessa Kirby. Nonetheless, advertisers come to television to build reach; television is widely acknowledged to be one of the most effective media for addressing a large number of people. That said, the frequency of seeing an ad is also important for brand-building and this is where duration-based commercial impacts are used alongside reach metrics. And when it comes to determining the cost of a campaign, the latter naturally takes priority.