Half a billion? One billion? Even more? Such are the grandiose predictions about viewing figures for India's meeting with Pakistan in the final of the 2017 Champions Trophy.

The incessant hype, of course, is a staple of the fixture. Nor is it limited to this game: every major sports match seeks to embellish viewing figures. It is the industry of "billion bollocks", as Nick Harris, editor of Sporting Intelligence, calls it. The most spectacular example was a Premier League fixture between Arsenal and Manchester United a decade ago. It was claimed that a billion could watch; they could have done, but only 27 million actually did.

It is a salutary reminder that the dazzling array of figures before a totemic sports fixture seldom pays much heed to facts. Only one sporting event in history - the opening ceremony of Beijing Olympics in 2008 - has genuinely drawn an audience of one billion people watching simultaneously, according to Harris.

"Reported figures for sporting events are usually inflated and include news, highlights and delayed broadcast - not just live TV audience," explains Krzysztof Kropielnicki from Sportcal, a consultancy. "Definitely don't trust any 'one billion viewers' figures for cricket matches which we have seen!" The trouble is, it is in everyone's interests - the sport itself, media covering it, and even brands associated with it - not to be too pernickety about the truth.

Recent India-Pakistan clashes - notably the semi-final of the 2011 World Cup and the group game in the 2015 World Cup - have routinely been credited with a billion viewers. But according to the ICC's own figures, the truth is a little less spectacular. The ICC figures find that there were 495 million unique viewers - that is, people who watched the game on TV overall - for the World Cup semi-final at Mohali six years ago, and 313 million unique viewers for the World Cup game in Adelaide - a drop-off largely explained by the time difference.

The Champions Trophy group game a fortnight ago was watched by slightly more, 324 million of which 201 million were in India - just over 60% - although far less than the common estimates that three-quarter of total viewers at ICC events are from within India.

So the figures may be nowhere near the billion commonly cited, yet they remain spectacular, especially when put in context. Consider this. In India, the entire 2017 IPL had a cumulative reach of 411 million: twice the Champions Trophy group game, but over 60 matches spread out over 46 days.

That pool match at Edgbaston was the latest in a series of drab India-Pakistan encounters. For the fifth consecutive year, the ICC fixed the draw to ensure the two met in the group stages if a global event; for the fifth consecutive time, India won resoundingly. And yet even the lack of on-pitch equilibrium has not eroded the appetite for watching the game. In India, the Champions Trophy group game rated at double the same fixture in the 2013 tournament, played at an identical time.

In a sense these figures are conservative too. They measure viewership on TV, but that does not include those who watch through illegal sources. Nor does it include the growing numbers who watch online, including through pirate streams, or those viewing through their smartphones. The ICC's exact viewing figures, then, implies a precision that, given the disparate ways in which live sport is absorbed, is impossible.

"Robust data collection and analysis simply doesn't exist," says Simon Chadwick, Professor of Sports Enterprise at the University of Salford. "There's an awful lot of hype in sport - around viewing audiences, numbers of fans etc - but very little 'scientific' evidence that the hype is warranted."

What of Sunday, then? The ICC estimate that the game will get 366 million unique viewers worldwide, watching for a total of 655 million viewer hours, and believe the figures could be even greater if - unlike previous matches - the game is close. Still, even then it is unlikely to approach the highest ever audience for a cricket match: the 558 million who watched the World Cup final in 2011; the average audience was 150 million, Harris finds, another record.

Even the allure of meeting Pakistan in the final of a global 50-over event for the first time is unlikely to match that, given the fact that it is in the Champions Trophy rather than the World Cup.

So, for all the claims, the game is unlikely to be genuinely record-breaking; it will probably merely be the third most-watched match in the sport's history. Still, taking into account all legal and illegal viewing sources on TV and online, those enjoying the game on wide-screen TV and masses being huddled around a single small set, it seems probable that about 400 million will watch at some point on Sunday. That's more than one in every 20 people in the world. Even if it proves less - though we'll never really know - this is a fixture that does not need artificial hype.