Every Tuesday, the Nielsen company publishes a popularity ranking of broadcast television programs that has served as the industry's report card dating back to when most people had only three networks to choose from.

And every week, that list gets less and less meaningful.

With DVRs, video on demand, game consoles and streaming services, tablets and smartphones, the way people watch television is changing and the industry is struggling to keep on top of it all.

Nielsen, which has long had a virtual monopoly on the audience statistics that drive a multibillion-dollar industry, last week took an important step toward accounting for some of the changes. Starting in September, Nielsen will begin measuring viewership through broadband devices for the first time.

"The ratings are a very one-dimensional look at what is happening," said Alan Wurtzel, top research executive at NBC Universal, "and we now live in a very multi-dimensional world."

Nielsen's weekly rankings count people who watch a broadcast TV show live or on their DVRs that same day through midnight on the West Coast. To be sure, this is still how most people watch television. Through separate, less publicized rankings, Nielsen also can track how many people see a program on a time-shifted basis. One ranking, which measures live viewership plus those who watch on DVR or video on demand within three days of the original airing, is what the industry uses to set advertising rates. Other rankings measure those who watch within a week, or even within a month.

Those numbers can present a much different picture of a program's popularity.

During the last week of January, for example, ABC's "Modern Family" ranked No. 12 for the week with 10.8 million viewers if you count just the people who watched on Jan. 23. But within seven days, 15.9 million people had seen the episode, enough to make it the third most popular show of the week. Fox's "The Following" finished a modest 15th place initially, but its audience jumped by 45 percent over the next week, enough to lift the show to fourth place.

Meanwhile, almost all of the "60 Minutes" viewing is done live. The CBS newsmagazine dropped from seventh place in the initial rankings to 15th after a week.

The time-shifted viewing can change a network's perception of a show. NBC would have likely canceled "The Office" years ago without this additional audience. "The idea of how many people are watching a program and caring about the show becomes increasingly important, and it is not reflected in the Tuesday report," Wurtzel said.

In a world where people demand information faster and faster, television executives are no different. The problem is, all of the changes in content consumption demand patience. Nielsen's report on how many people watch a show within seven days isn't released until three weeks after a show first airs.

"We have to basically train the entire industry to no longer look at the fastest information, which is preliminary and not necessarily reflective of what the reality is," Poltrack said.

Nielsen says it regularly discusses how it releases ratings with its clients and there's been no consensus on change. Most people watch their favorite shows as quickly as they can, said Pat McDonough, Nielsen senior vice president of insights and analysis.

"The one thing most people don't think about is a lot of the additional viewing is rolling out slowly over time, and right now live plus same-day viewing is the best way to measure," she said.

Networks dispute the notion that things are changing slowly, although they are happy that Nielsen will soon be able to estimate how much television is being watched on broadband.

Later this year, Nielsen hopes to roll out a pilot program to identify what people are watching on iPads. It's unclear when this technology will be available for other tablet brands or for smartphones.

The company measures some online video streaming and includes it within its reports. However, this picture is partial, too. Nielsen can measure streamed programs only if they have the same commercials shown on TV, and not every website does this.

People are increasingly spending time catching up on series they've caught on to midstream. No one really knows who is spending an evening watching three episodes from the first season of "Homeland" instead of live TV.

Nielsen has an oblique way to illustrate that binge viewing is a reality: When AMC's "The Walking Dead" returned from a hiatus on Feb. 10, the 12.3 million people who watched that night was a series record. That episode was the ninth most-watched television show in prime time that week, but it would have taken some investigation to know that. Nielsen ranks broadcast and cable shows separately.

Cable networks are in no hurry to change that because, with the exception of the biggest hits, even relatively unsuccessful broadcast programs get more viewers than cable.

There's a similar dynamic with PBS. The public broadcasting system generally doesn't pay Nielsen to have its programs rated, although it will on special occasions. The 8.2 million people who watched the third-season finale of "Downton Abbey" on Feb. 17 was more than anything seen on ABC, Fox or NBC that night. No one would have known that unless they'd seen a report generated by a PBS press release.