The co-ownership of a parcel of land, or land fractionation, on a dozen Indian reservations has doubled from 1992 to 2010. That’s according to a recent study which compared 2010 statistics on land fractionation to a government study from 1992, the only publicly available study of fractionation.

Fractionation happens when several heirs inherit undivided interests in the same allotment of land. Over generations, allotments can end up being shared between dozens of owners.