My guess would be quality control, it appears iCarAsia wants to...

My guess would be quality control, it appears iCarAsia wants to mimic Carsales with great UI (User experience) and that involves removing listing's as they get sold.

Carsales does this via a pay per lead model whereas dealers have incentives to remove the listing once the Car has been successfully sold.

The growth in leads is the key indicator of where the business is going, and their is no doubt monetization is happening and revenue should rapidly increase over the years. Their path to profitability from the investor presentation suggests 2016. Though it appears this is happening sooner than later.

I'm sure there are also seasonal factors in the markets that would effect listings, and supply and demand etc.