The problem with any "average" pace ride listing, for groups where relatively random strangers show up, is that you can't really define average for what. The course for that day? That would require everyone having ridden that course previously. Average speed for riding on flat ground? -- that might work in eg Florida, but otherwise you start hitting hills and some riders might be able climb at 1/2 the speed of the posted ride's pace, others at eg. 1/4 of that. Downhills, different comfort levels. Some club rides I've seen the pace set at some range of watt/kg value. That has its own limitations.