colonias. Incentives such as microcredit programs are being implemented which then allow families to reach acceptable levels of housing quality. The model addresses equality by setting a standard for housing based upon compliance of available resources, and would commit the government and people towards the common goal of sustainable housing. However, this does not mean that governments do not have obligations once a certain standard is reached. The progressive realization model requires continual progress in a relationship between law and society, which directly corresponds to the choices of those living in colonias. Enhancing the lives of the colonians through policy has proven to be difficult and slow. Funding for infrastructure projects for colonias is contingent on defining a "colonia", and establishing effective criteria for this purpose has proven to be a challenge. The Farm Housing provisions of the United States Code define a colonia as a community that (1) is in the state of Arizona, California, New Mexico, or Texas; (2) is within of the Mexico–U.S. border (except for any metropolitan area exceeding one million people); (3) on the basis of objective criteria, lacks adequate sewage systems and lacks decent, safe, and sanitary housing; and (4) existed as a colonia before November 28, 1990. Other definitions are used by specific governmental agencies (e.g.: HUD, USDA, Environmental Protection Agency [EPA], and the Texas Code). Many scholars criticize the existing federal criteria as being too broad in that most definitions of colonias are based on the archetype that exists on the border in Texas. While colonias in Texas are known for being peri-urban settlements with mostly Hispanic dwellers, settlements in California are located in old rural towns with ethnically diverse populations. This has hindered colonia infrastructure development in California. Criteria have also been described as too narrow, relying on numeric values to determine whether a settlement qualifies. Under the U.S. Department of Housing and Urban Development (HUD), funds designated within the Community Development Block Grant (CDBG) were to benefit colonias along the Mexico–U.S. border, defined by various numeric values. However, colonias such as those in Riverside and San Diego counties are disqualified from the CBDG for being within metropolitan statistical areas (MSAs) with over a million people. Similarly, the U.S. Department of Agriculture limits its colonias to settlements of no more than 20,000 residents, disqualifying the majority of communities seeking funding in California. The EPA's definition of colonias derives from NAFTA, which