My guess is around 5% of the freight would have to go on a straight truck if it were not for the existence of Sprinters. Part of that comes from load board and load bookers and dispatchers, and it fits with what I see out here in general. When I was in a cargo van, it sure seemed like it was a much higher percentage, tho. Seemed like every time I turned around I was having to partially break down a skid to get it into the van, then rebuild it inside the van, and then reverse the process on the other end. Or I'd get there and find that it wouldn't fit at all. Now I carry Sprinter loads, but nowhere near as much as 5% of my freight. I can only haul two skids, tho, and there are some three and four skid loads out there that are put on Sprinters. All in all, it's about 5%. It might be as much as 10% of the non-straight, non-tractor freight, but I don't think so. That's an awful lot of freight when you think about it. The number of cargo vans out there utterly overwhelm the number of Sprinters, and if the percentage was as significant as 10% then we'd see a lot more Sprinters.
Of course, there are some carriers who cater to shippers who "build" Sprinter loads, who build bigger loads specifically for Sprinters so they can ship more for less money than having to ship it on a straight truck. Those folks will see a very high percentage of Sprinter loads. But overall, industry-wide, I'd say 5% is pretty close. It's not nearly as high as I was hoping, that's for sure. But my Sprinter gets me a few loads per year that I wouldn't have otherwise gotten.