An observation by one Android developer suggests in-app billing isn't the only change Google has made to Android Market in recent weeks.

Geoff Cook, CEO of social networking site myYearbook, believes the search giant has adjusted the the store's ranking algorithm, causing apps to move up and down the tables when, in reality, the level of downloads has remained the same.

Rules of engagement

After witnessing his Android app shoot from #63 to #11 in the Top Free Social Category, Cook checked the daily install numbers only to discover no significant change.

The explanation for this seems clear: Android Market is now factoring in engagement when ranking applications.

Citing the performance of the myYearbook software and his game Tic Tac Toe, Cook asserts that a complex ratio of DAU to MAU is underpinning the Android Market's new algorithm, rewarding an app's stickiness as highly as its initial take-up.

Such a modification would certainly make sense for Google, given the introduction of in-app billing last week, though the company is yet to offer official comment.

With Android developers facing perennial problems with piracy and a customer base unwilling to pay premium prices, the DLC model is regarded as a quasi-saviour, so measures taken to promote in-app purchases and long-term engagement could well be welcomed.

[source: GigaOM]