The supply of digital uniques has eroded over the past year, but most of the decline has come from desktop vs. mobile, according to an analysis of the past 12 months of data from the Digital Traffic Index.
The index, a collaboration of Jumpshot and MediaPost tracking the supply of daily unique users on mobile and desktop screens, fell to an 85.38 on Friday, July 8. That’s down from an index of 112.05 on July 10, 2015, the equivalent Friday a year ago.
The index, which was benchmarked at 100 on Jan. 1, 2015, is drawn from a base of 115 million U.S. digital users that inform Jumpshot’s measurement. While seasonality and day of wee, can influence the peaks and valleys of digital’s unique user base, the index is intended as a means of measuring the supply over time.
While the total index value declined 24% year-over-year, the decline is much more attributable to desktop than mobile users.
The index for daily unique desktop users fell to 54.35 this year, a decline of 54% from 118.06 a year ago.
The index for daily unique mobile users, by comparison, was down 29% to an index of 76.38 this year vs. 107.10 a year ago.
Not surprisingly, total pages viewed -- a key source of digital ad impressions inventory -- also crashed during the same period, falling to an index of 63.43 this year from an index of 110.67 a year ago.However, the average amount of time spent per user, as well as the time spent per page -- a potential measure of engagement -- showed a corresponding increase over the period, suggesting that digital media users may be growing more discerning about which content they engagement, but more involved with the content they do engage with.