Not source checked but it appears that 96% of trucking companies have 28 trucks or less and 82% operate with less than 6 trucks.

http://www.truckingoffice.com/2012/interesting-trucking-indu...

Would be interesting to know how large proportion of trucks were in the 4% largest trucking companies. If that turns out to be a large quantity, then the 96% figure no longer seems that big.

Vast majority have far fewer than 10 trucks.

Define big enough, even owner/operators generally do their own servicing and repairs.