A quick tip this one. Whenever you want to group a reporting query by date (by month, day, year) you can use the following approach in MySQL
SELECT DATE_FORMAT(yourdate, '%Y-%m') AS grouping_date COUNT(id) FROM yourtable GROUP BY grouping_date;
Change the date format to whatever date quantum you want to report on, i.e. just have '%Y' for a yearly grouping, or have '%y-%m-%d' for a daily one.