I did a fit for the histogram based on the data above for the period from the beginning of 2009 to the present and when logs of the counts are used the curve is fairly linear. The fit yields an empirical equation for the annual number of earthquakes in M 0.25 intervals.
The numbers can be seen in the table below. The first two columns specify the width of the interval, the third column is the expected number of earthquakes in the interval per year and the last column is the expected number of days between earthquakes in the given interval. There are very few M 7+ earthquakes in any given year.