Take the performance of the excellent US legal-political-domestic drama The Good Wife. The episode that aired on October 17 was watched by a mere 343,000 viewers, a disappointing result (seriously) for a prime-time drama. But a week later, Ten was able to share the good news that a further 182,000 people had watched the show in the following seven days, giving it a 53 per cent audience boost to an almost-acceptable 525,000 viewers.

If you needed proof time-shifting plays havoc with the schedule, this was it.

Indeed, Ten has no shortage of proof. Across its second season, Homeland has averaged a 25 per cent boost on consolidated viewer numbers (those who watch a program within seven days of its initial broadcast). Puberty Blues averaged 20 per cent over its season, Offspring 21 per cent. That episode of The Good Wife was an anomaly, but not by much. Throughout this season it has picked up an additional 30 per cent a week through time-shifting.

Ten is not unique in this respect, but the fact its programming tends to draw a younger and more tech-savvy audience means it is more exposed to the change in viewing patterns - and not just in ''official'' time-shifting, either. When Ten ran two episodes of Homeland back-to-back a few weeks ago, it did so largely to minimise the gap between the show's US airdate and its local screening (down from 13 days to six) in a bid to discourage illegal downloads.

BitTorrent is the bane of the broadcasters' existence, but the internet and other digital distribution platforms may yet offer them salvation. The challenge, though, is in monitoring the audiences attracted to their content through sanctioned channels (their own catch-up services) and monetising it. That is, delivering to advertisers a real and measurable audience.

Ten claims the September 16 episode of Puberty Blues attracted 880,000 video views online over the following seven days. That's a big audience, if it can be substantiated. But to gain a sense of the challenge, consider this: a single hour-long episode is broken into six segments online, meaning the number of viewers could be expected to be about 146,000. But there is no guarantee they all watched the entire segments - or, more to the point, the advertisements that preceded them.

Having an audience that watches advertising is at the heart of the commercial free-to-air television model, and downloading and time-shifting pose serious threats to it. The ratings agency OzTAM has tracked time-shifted viewing since late 2010, when 4.5 per cent of viewing in the 3035 households in its national database was done outside live viewing. In its most recent report, due to be released today, that figure has risen to 6.77 per cent. Because viewing patterns fluctuate with the seasons (we watch more TV in winter than in summer), a like-for-like comparison is more useful - and on that measure, time-shifted viewing grew from 5.57 per cent in the second quarter (April to June) of 2011 to 7.28 per cent in the same quarter of 2012 - a 31 per cent rise. The base is small, but the pattern is clear.

OzTAM claims the consolidated audience figures do not distort the way we're watching. If you skip through the ads on a 60-minute drama and watch roughly 45 minutes of programming, you will constitute 0.75 of a viewer on average because the data is tracked on a minute-by-minute basis. Yes, it's true that could mean a 150,000-viewer gain is actually a 200,000 audience, but if those 50,000 other people aren't watching the ads they don't count.

The real challenge, though, is the viewers outside the box, and so next year OzTAM will begin to monitor the online activity of a small subsection of its sample. In 350 homes, viewing of TV content online will be monitored.

Nine is also developing its own in-house system, called IRIS. It aims to track viewer activity online as they're watching TV, in a bid to deliver more targeted information to advertisers about the effectiveness of their campaigns. It will be a case of Big Brother watching you watching Big Brother, and posting about it on Twitter.

And given that three-quarters of people are now using a secondary screen - a smartphone, tablet or laptop - while watching television, you can be sure Nine won't be alone for long.