Statistically:
– at least one planet is retrograde more than 92% of time
– only 8% of time none of them retrogrades.
– The biggest group (56%) of people/charts has 2 or 3 retrogrades – these are the “standard people” who fit well in the world as they are the majority.
It’s almost a regular “normal distribution”, however, to have no retrograde planets is still more likely than to have five in retrograde.
Six or more planets in retrograde is quite rare. Those with 7 retrogrades are way below the “statistical error” – so they get marginalised by default.