Since we launched Article-Level Metrics in March 2009, we've been keeping a watchful eye on our online usage data. We look for anomalies, investigate them and clean them up. This ongoing process is essential to preserve the integrity of the data and is painstaking work, but thankfully we've been ably assisted by our community who we encourage to report issues by sending a note to email@example.com.
We have just added some previously missing log files to our usage data (from the period November 2009 – April 2010) which has resulted in an increase in the usage data for most articles.
In addition, we have cleaned up some unauthorized spambot usage (which had significantly over-inflated usage data for approximately 30 articles) – this has resulted in decreased usage being displayed on about 500 articles.
We know that many of our authors watch their usage data carefully (as do we) and we hope you appreciate our efforts to keep this data as 'clean' as possible.