We recently changed the way clicks are being tagged and reported for aStore. This explains the recent drop in clicks Associates using aStores have observed in the Associates Central reports.
Until recently every visit to and click within an aStore was reported as a click in Associates Central. So, if a user visited the first page of your aStore, then visited a product detail page, placed the item into the cart, and proceeded to checkout on Amazon.co.uk your aStore reports would show four total clicks for one order.
All other Associates links are tracked as clicks and tagged only if a user comes via your referrals to the Amazon website. In order to maintain consistency across the different Associates tools we have updated the aStore tracking to follow the same approach.
So, an aStore "click" will now be reported whenever one of your site visitors is referred to Amazon through either adding something to the aStore cart and proceeding to checkout or by visiting Amazon.co.uk via one of the links embedded in the store (such as the "new and used" link, the search link, etc.).
Therefore you can expect a drop in the number of clicks showing up in your reports, but you should also see an increase in the conversion percentage.
We realize this creates a gap in tracking the traffic to and within your aStores, and our aStore team is actively exploring ways to enhance the reporting functionality. We'll keep you posted as things change.