Chris A. a11n

This plugin requires PHP 5.3 or later, please check with your web host if you’re unsure.
Adoption uses the timezone that is set in the WordPres admin panel. Ensure you have set your local timezone in Settings > General.
Features:
<ul>
<li>Displays a bar chart with registration statistics for predetermined time periods (e.g. this week, last week, last 3 months, last 12 months, etc.)</li>
<li>Displays a “Quick Statistics” section which includes a summary of user registrations for popular time periods.</li>
<li>Easy to use, tidy and fits in with the overall WordPress user interface.</li>
</ul>

Adoption

Adoption displays user registration statistics in a neat dashboard widget

Adoption vs Visualizer: Tables and Charts Manager for WordPress