Hacker News Reader

The post was written by a 3rd party and not Instagram. The last section of the article explains how they managed to get the data:

"Four things allowed us to conduct this analysis: Instagram’s new API, their use of incrementing ID numbers to represent users and photos, the central limit theorem"

View on HN

Unfortunately, this isn't very rigorous - the dataset can easily be gamed by instagram.

If the Instagram guys have read this http://en.wikipedia.org/wiki/German_tank_problem , they might be having a good laugh...

Well my point was more that Instagram exposed enough data such that RJ Metrics were able to get access to enough information to extrapolate the cohort retention rates.

Reply on news.ycombinator.com