The App Store Is Crazy, Certified Crazy!

We couldn’t help but notice our community being all a-twitter about huge, unexpected rank changes in the last two days. We thought we’d break out the old calculator and examine it a little bit.

As you know, appFigures tracks top-200 ranks in App Stores around the world. We took this data and looked at each app’s changes by comparing the hourly change of each app and taking the largest hourly move per day.  We added up all the apps that had a big change > 50 (up or down) and compared those numbers to the same days of last week. The goal was to get a picture of high-magnitude changes in rank, the sort that would seem unexpected. The numbers spoke and told us that something was not right.

Tuesday was slower than usual

Wednesday, and Thursday were crazy!

Let’s get numeric:

During a normal day, 5.77% of apps experience an hourly rank change of more than 50 places (up or down). On Wednesday, that number shot up to over 70%, indicating that it was a particularly volatile day in terms of high-magnitude hourly moves. Thursday experienced similar churn, with nearly 50% of apps experiencing these high-magnitude changes.

Here’s an overview of the last 30 days on the App Store. Look at that NBA-level jump…


Daily % of apps that moved 50 or more places in one hour.

And here’s a direct comparison to last week:


Apps that moved 50 or more positions in one hour.

Then we dove a little deeper into the nature of the changes, taking not only hourly rank movements of 50+, but breaking them down into four groups: 0-50, 51-100, 101-150, and 151+ places.  On normal days, 94% of apps see no hourly rank change greater than 50 places. A bit less than 2% see a shift of 51-100 places, and the same for 101-150 and 150+. On Wednesday and Thursday, only about 40% of apps stayed within 50 places, with around 20% seeing a change of 51-100, and likewise for 101-150 and 150+ places. Take a look at the breakdown:

This is what a normal day on the App Store looks like:


Maximum change in rank for 1/25-2/1

This is what Wednesday and Thursday looked like:


Maximum change in rank for 2/3-2/4.

We were puzzled as to why the big movers were distributed relatively uniformly (in that the percent moving 51-100 places ~ 101-150 places ~ 150+ places), rather than showing a more normal distribution, but that’s for another day.

Another peculiarity we found on 2/3 and 2/4 was the average highest hourly rank change per app. That number was consistent around -8 places up until 2/2. On Wednesday and Thursday it jumped dramatically to around +25 places each day. So, though the app store has shown big swings on those two days, an app’s biggest hourly swing is on average 25 places up.

Well that’s it for now, we’ll have some more analysis coming soon.

  • leberwurstsaft

    Please, keep us updated. This were two really weird days, indeed!
    We're lucky to have companies like yours that have quite some insight into a lot of data to analyze this kind of irregularities.

  • aaronwatkins

    Could it have something to do with alot of smut apps, many of which were high ranking, being removed from the app store, casing apps below them to move up en masse?
    http://theappencypress.com/2010/01/31/the-ipad-

  • Pingback: What happened to the AppStore last week? « Spiralstorm Games()

  • Rob

    The normal mean change of -8 per app I think would be explained by new apps being added to the list. For example, if 16 new apps enter the list, evenly spread between positions 0 and 200 that should give an average change of -8 for the apps already in the list.

    If the new apps all enter at the top of the list, then only 8 are needed, but that seems unlikely ;)

    Anyway… So if you saw an average change of +25, (33 more than the usual -8) that suggests that about 66 apps were removed from the list.