In the 2007 census, 68.5% of production units were under the social regime - ejidos - and accounted for only 34% of land, 29% of farms were under the private regime, accounting for 61% of land (Table 17). As it turns out, about 75% of farms of less than 20 hectares are in ejidos, while 75% of large farms over 100 hectares are privately held. It was only in 1992 that the Constitutional Ejido Reform changed the situation, strengthening property rights. However, despite reforms, this communal property still constrains the agricultural land market.