This is a good article discussion the main reason of failure and success for mobile apps developers. The apps with success stories on the app stores who, are around 20% of whole apps, are investing 25% of their time and resources on marketing activities which in response is increasing the number of downloads for their apps. Most developers, 80%, are not spending seriously on marketing although they believe downloads are increased by marketing.
These statistics are collected by app-promo.com which is providing promotional solutions for mobile application development, although the result is supporting the business of app-promo but it is also showing the real state of developers who are competing in the app stores. The original article is available on the link: http://app-promo.com/wake-up-call-infographic/