Let us face it: getting consumers to install a new application can be a difficult proposition. This year saw the highest single increase in apps listed on the App Store since 2008, with 25 percent more apps ? about a half-million ? listed than in 2015. 

However, on an individual level, while users average around 25 apps per device, they only regularly use one to five apps per week. This indicates the challenge that media planners face when focusing solely on installs. 

When it comes to modeling app engagement, the good news is that there are sophisticated app tracking software platforms such as Tune, Appsflyer and Kochava that allow agencies and performance marketers to drive measurable installs that can be monitored for quality. 

The fact is, the app gold rush is only just beginning. More agencies are being approached by their clients with requests for high-volume install (CPI) campaigns. 

Installs are quickly becoming the ultimate mobile currency and with apps becoming an integral strategy for most of the world?s largest brands, this trend will only increase.

With this in mind, here are three things that media planners need to know to run effective CPI campaigns for their clients:

1. Start with the right audience

With more than 4 million apps across iOS and Android, finding the right audience is key. 

Always start by targeting users who you know have used similar apps as yours. 

If you are promoting a travel app, target users who have installed Hotels.com or Yelp.com. 

Promoting a casual game? Start with users who have downloaded Candy Crush or Clash of Clans. 

Tools such as Facebook provide these kinds of targeting capabilities natively, but if you are looking for more scale, many ad vendors have created tools that allow you to target app audiences by the apps they have installed. 

By starting with a targeted audience, you are going to get much better CPI results as well as better app engagement. 

2. Know your metrics and re-engage your users 

While an install is one thing, engagement is another. 

That is why it is important to know what kind of metrics you are looking at to determine what ultimately defines success post-install. 

For example if you are measuring engagement you may want to look at metrics such as:

o Number of app sessions

o Retention rate

o Daily active users (DAU)

o K-factor, or the average number of users each active user refers to your app

The other thing to consider about post-install behavior is that it takes a user a few tries using an app before it becomes part of his or her app regime. 

For example, you can look at app session data to create cohorts of users who showed lower activity during their initial sessions and re-engage them with retargeting campaigns. 

Attribution analytics is one way to get deeper insights into characterizing user behavior post install. Tune provides a great summary on postbacks for re-engagement campaigns and how some organizations are tracking re-engagement data. 

3. Optimize towards post-install events or consider a CPE campaign

Installs are a perfect commodity for marketers and brands alike. They are trackable, scaleable and a wholly owned channel directly tied to a consumer. 

But an install is really a means to an end. It is only as good as the consumer engagement it enables. 

All of this is to say that while installs matter, engagement is where the value lies. 

Work with your client to define a few actions that signal a quality user. 

If the app is a game, what level do users get to before they become more likely to play? 

If the app is for shopping, how many searches indicate that a user might be likely to buy in the future? 

Once you have determined an action post-install that signals quality, you can use your tracking partner to send your ad vendor a postback that signals that they have found a quality user. 

This communication allows your CPI vendor to actively optimize their acquisition campaigns towards users who are more likely to complete desired behavior.

Super-savvy companies such as Uber and Lyft are actually bypassing the install altogether, and instead working with vendors to offer a cost-per-engagement (CPE) model where they only pay for users when they take their first ride. 

WHEN IT COMES to CPI and any results-oriented marketing program, the guaranteed promise of results is always compelling. 

However, while installs are a good barometer for engagement, it is the post-install engagement metrics that tell the deeper story on why a user chooses to use an app or not. 

As app stores become increasingly saturated with apps, media planners will need to get smarter on how to derive meaningful value from their mobile app engagement strategies.