Pay television is big business, but nobody seems to agree quite how big. Contrary to popular opinion, the number of pay-television subscribers is growing. It could be approaching a billion households worldwide, but recent reports appear to disagree on when that figure will be reached.

Digital TV Research estimates in its Digital TV World Household Databook that there will be more than a billion digital television households by the end of 2014, with 886 million homes subscribing to television services.

ABI Research estimates in its Pay TV ARPU and Revenues report that there will be over 920 million pay television homes worldwide by the end of 2014. The number is forecast to reach 1.1 billion in five years. Assuming linear growth, that implies reaching a billion sometime in 2017.

Parks Associates expects that the number of households with pay television will exceed a billion by the end of 2015. Its report titled Under Attack: assessing new threats to Pay TV considers the competitive threats to the traditional subscription television ecosystem.

One might expect there to be general agreement on the number of pay television subscribers worldwide. Yet it seems there is considerable variance across reported figures and forecasts.

The reality is that despite the apparent precision of the numbers, most analysts rely on some degree of estimation based on assumptions.

One reason for this is that not all service providers disclose subscriber numbers and even among those that do there is no standard way of reporting the data.

Most information providers charge thousands of dollars for access to their proprietary databases and market forecast reports. Some do not even list their prices.

It can be very confusing for anyone trying to understand the pay-television marketplace. Even headline figures from many research companies are not in the public domain. Yet there is considerable variance across the figures reported.

So informitv has been collating its own data to track television industry trends and inform its clients. Now we are making this more widely available.

The informitv Multiscreen Index tracks a hundred leading pay television services worldwide, based exclusively on operator reported figures for digital subscribers.

The aim of the Multiscreen Index is to provide an objective index against which to measure actual change, rather than assume general industry growth.

Rather like a stock exchange index, companies are either included or not, based on published criteria, and ranked accordingly.

The top ten operators account for more than a third of television subscribers to companies in the index.

The hundred services in the index collectively represent over 330 million subscribing homes worldwide, covering major operators with over a million subscribers.

Where are all the others? Some are in markets like China, where there is less transparency around subscriber numbers. Some are among smaller operators with less than a million customers. Some are still analogue television customers that we do not currently count, but have the potential to convert to digital.

We can be confident about the reliability of the numbers in the Multiscreen Index because we have researched them from primary sources. However, there is surprising variation among other estimates and forecasts of the total size of the market.

The informitv Multiscreen Index provides an index of reported subscriber numbers across the main pay-television services, with top ten tables by various categories. It is easily accessible, with access to quarterly figures for personal use starting at just £100.