Many Android phone models do not get the latest operating system updates for months after the official update is completed, due to delays by the provider or hardware maker, either of which may want or need to address layers of customization they've made to the generic Android distribution. Two weeks ago, Google published its own stats based on Android users visiting the Android Market software store, which reflected active users who download apps, and presumably would be more likely to be up to date. Its figures indicate that only 27.3% of Android Market visitors are running the latest version of the Android OS, while nearly 70% are still using Android 1.1, 1.5 or 1.6. That prevents those users from being able to download the latest apps, including Twitter's new client for Android, which requires the 2.1 firmware version.