How does your advert refresh rate affect revenue from your app?

First of all a quick run through of the mobile ad industry jargon:
Requests - How many times an app requests an advert from an ad provider.
Impressions - The number of ads actually shown to users.
Fill rate - The percentage of impressions compared to requests.
Click Through Rate (CTR) - Percentage of impressions that result in a click.
Estimated cost per thousand impressions (eCPM) - How much an advertiser will be charged for 1000 advert impressions or how much a publisher will be paid for 1000 impressions.

For the past six months I have been earning money by showing adverts in my game "Cherry Chaser".  I began with the refresh rate (recommended by Google) of sixty seconds so my game would contact the advert provider and request a new ad every minute.  After a while I decided to make the adverts somewhat less intrusive by changing the refresh rate down to 120s, or once every two minutes.  This is the maximum interval you can put into the Admob interface.  This had the obvious effect of reducing the number of overall ad impressions by about half and roughly doubling the CTR and ecpm.  The outcome being that revenue stayed roughly the same but the number of adverts I was showing was halved.

I kept the higher refresh rate as I decided that a good general principle would be that showing less adverts is less intrusive to the user.  I don't know how true that is, after all is it better to show one bad advert for two minutes or a good and a bad one for one minute each?  It probably doesn't make any difference either way and the net effect is the same.  One thing I can say though is that less advert requests does mean less network traffic for the user and some mobile users have quite tight monthly data budgets.

Jump forward to the past two weeks and I released my new game "Super Snake Slot Machine".  When publishing it I forgot to set the refresh rate in the Admob interface and it got left at a setting of "no refresh".  What that meant was that an advert was requested when the game started but then no new ads were shown after that.  The effect was that the CTR for Super Snake was about 5% compared to the 1% CTR I was regularly getting on Cherry Chaser at a 120 second refresh.

I had nothing to compare against so I set the refresh rate on Super Snake to 120 seconds for a couple of days and CTR plummeted back down below 1% whilst the number of impressions more than quadrupled.  The overall revenue dropped slightly at a time when I would have expected it to be rising in line with the number of active installs.  After setting the refresh rate back to "no refresh" the revenue rose again, although only in line with the growth of the user base.

I've now also set Cherry Chaser (which has 130,000 active installs compared to Super Snake's 4000) to also disable the refreshing of adverts.  This has had no noticeable affect on overall revenue which has remained about the same.  Number of ad impressions has dropped by a quarter and the CTR has risen by the same factor of four.

An unknown aspect for me here is how your CTR affects the quality of the adverts that are sent to your app.  I've heard hints that a higher CTR will mean you are sent ads that give higher profits.  It's very hard to tell if that is a real effect because you only have the one figure which could be affected either by the quality of the ad or the length of time it is displayed.  I've read that CTR is a very important factor in Adwords ads with higher click words drawing a higher revenue.  I don't see that the same principle will automatically apply in the mobile app advertising space though.

In conclusion it seems to be better to have higher CTR and a lower number of impressions by completely disabling advert refreshing.  If nothing else it reduces the bandwidth usage of the app slightly.  It may just be something about my own app that means this works and I can't rule out that a coincidental fluctuation in advertising rates has misled me to believe that the revenue is slightly better.  I feel somewhat like I'm swimming against the tide of convention by disabling advert refreshes but so far nothing in the figures shows it to be a bad decision. 

I'm happy to say that the latest production from Exobyte games has now been successfully launched on the Google Play store.  This posting will be a fairly lengthy description of the process of going from finished code to a released game.

Super Snake is based upon the same core engine as the highly successful Cherry Chaser slot machine game.  After making Cherry Chaser I had the urge to create a feature ladder style machine and this is the result.  I think it plays better than Cherry Chaser, collecting numbers on the win line makes it a more addictive experience.

The process began when I had a version of the code that was just about done and worked well in a testing environment.  If you want to know more about the development process before that I can suggest the book "Beginning Android Games" by Mario Zechner.  I'd also suggest getting hold of the LibGDX games library for Android also created by Mario as that shortcuts a lot of the steps described in the book.  It's worth reading the book all the way through though just so you understand the engine you're working with.

The first thing that I did was begin working on the graphic components that are required by the Play Store.  The main graphics required are a 512x512px play store icon (see image above) and a 1024x500px feature graphic.  It also asks for a 180x120px promo graphic for which I use a cut down version of the feature graphic.  The promo graphic seems to only be used if the game gets promoted on the front page, I'm not expecting this to happen as a slot machine isn't really unique enough to be featured, but I put one up just in case.

When promoting Cherry Chaser I gave thought to the best style of icon to represent the game in the store.  People browsing the store will make a decision to click almost entirely based upon that image so I wanted mine to be as descriptive as possible.  The most important thing I felt was that the icon looked like what the game was supposed to represent, that is a slot machine.  I also wanted it to look distinctly like the european "pub style" slot machine that my games were inspired by.  To create the icon I took a generic photo of a real fruit machine and overlaid a screen grab of my game onto it, cutting and skewing the image until it looked right.

Once the graphics were ready for the Play store I loaded the game's project file into Eclipse and used the export tool provided by the Android SDK to create an APK file for installation on phones.  Part of the export process is to sign the games with a key, that's the thing that allows games to be "trusted" by phones and the bit that isn't needed if you tell your phone to install applications from unknown sources.  The keys have an expiry date, I set mine to 75 years as I'm an optimist.

Next we go to the Play store developer console and hit the button marked "upload apk".  Here's where we provide Google with with all the graphics they require for their listing.  We also set the title and descriptive text.  The generally accepted rule here is to have your primary search terms in the title text, thus the title of my game is "Super Snake Slot Machine" as opposed to just "Super Snake".  The next rule is to scatter other target search terms casually through your descriptive text.  I try to do this within the description keeping things readable but I see other apps just openly listing search keywords in the description.

At this point I apply a tip I learnt about getting your app as wide a distribution market as possible.  At the top of the listing details there is an option to add text for other languages.  If you go into this option you can select every other language listed there and then check a box to populated the text automatically with auto-translated text.  This is going to be better than nothing when presenting your game to people that do not speak english and so there seems to be no reason not to do it.  You may have to work with the word limits on some sections but trying different words usually works.

After that you simply check the consent buttons and then hit the publish button.  Your game will appear on the Google Play market place about an hour or two later.

At this point I hit a problem, my in-game links to the Google Play store were all broken.  An investigation of the problem revealed that the package name had a typo, it was called "net.exobyte.supernake" in the manifest file.  Unfortunately the package name is the one thing that is fixed permanently and can't be deleted so I had to fix the manifest and then go through the whole publishing process again whilst also unpublishing the broken version.

Once the game was up and published I did a final step which was to create a gameplay video.  I could have done this before I published but I sort of see it as the icing on the cake.  I used FRAPS to capture video direct from the game running on my development PC (LibGDX allows you to develop in desktop java using JOGL) and the Corel Video Studio to put all the clips together into a montage.  I'm quite pleased with the result and hopefully it will drive a few more downloads.

So now I am done and 24 hours have gone by since I released the game.  Right now I have no idea if it will be successful or be lost in the depths of the Play store.  When I released Cherry Chaser there were less than 20 games in the "New Free" tab in the Cards and Casino category, today when I looked there were over 150 games listed there.  I don't know if that's because of a change in the way Google poll the listings but it seems to suggest that the competition in this niche of the market has heated up substantially.

Now it is all down to whether I get good user ratings.  Currently I have two five star ratings and one one star rating.  That's similar to how Cherry Chaser began so I'm not going to read too much into it.  I think I've made a fun and worthwhile game, I hope enough other people do too. 

Find Super Snake on the Google Play store