• by Joe Mandese  @mp_joemandese, February 10, 2016

The backfield was in motion on Super Sunday as the supply of digital unique users shifted to mobile from desktop. The supply of mobile unique users rose to the highest point in nearly five months on Super Sunday -- reaching an index of 113.9, according to the Digital Traffic Index, a collaboration of MediaPost and Jumpshot, measuring the supply of digital unique users across mobile and computer screens.

The last time the mobile index was higher was on Sept. 27, 2015 when it reached 115.7, and generally speaking the Super Bowl spike in mobile uniques comes during a seasonally low period. The 12-month high was an index of 120.7 on June 20, 2015. The 12-month low was an 80.8 on Jan. 28.

The index points translate into the availability of real people and their devices, and for all practical matters, represents a way to look at the supply of human attention to digital screens each day. It is based on the actual supply of unique users available daily in Jumpshot’s panel of hundreds of thousands of people and their devices.

The index is available continuously and is adjusted daily to reflect the equivalent of a daily trading day -- seven days a week. Periodically, when news events occur or when there are shifts in the baseline index that represent potential news, MediaPost reports on the market movements related to it.

To understand the impact of the index in real human and device terms, Jumpshot provided some rules of thumb for framing the magnitude of shifts in the index values:

A 1% change in the mobile unique index equals about 2.8 million mobile devices.

A 1% change in the desktop unique index equals about 1.8 million desktop devices.

A 1% change in the total uniques index equals about 4.6 million total devices.

Projecting how those devices correlate to the supply of individual unique users is difficult, because different people use different devices differently to access the Web and other digital media. But Shaun Rivera, a senior analyst at Jumpshot who tracks the index, offers a good rule of thumb:

“Based on the assumption that an individual owns 1.86 devices (mobile, tablet, and desktop/laptop), we expect that a 1% change in the index would affect about 2.5 million people.”

Based on that logic, there were roughly 2.5 million more people available on digital screens on Super Sunday, as the index climbed nearly 1% from the previous Sunday. (Weekday-over-weekday is the right way to look at the index, because it is most representative of digital media usage patterns vs. day-over-day).

And most of that increase came from mobile, not desktop. How much that increased mobility was a function of the Super Bowl -- possibly people traveling to other people’s homes or public places and using their mobile devices while doing so -- may never be known, but it is clear that Super Sunday has an impact on the behaviors and access of American consumers, especially on their digital devices.