income, any rural area, and any Indian area. (II) Rural area For purposes of subclause (I), the term rural area means any non-metropolitan area, or any rural area as defined by section 520 of the Housing Act of 1949, which is identified by the qualified allocation plan under subsection (m)(1)(B). (III) Indian area For purposes of subclause (I), the term Indian area means any Indian area (as defined in section 4(11) of the Native American Housing Assistance and Self Determination Act of 1996 ( 25 U.S.C. 4103(11) )). (IV) Special rule for buildings in Indian areas In the case of an area which is a difficult development area solely because it is an Indian area, a building shall not be treated as located in such area unless such building is assisted or financed under the Native American Housing Assistance and Self Determination Act of 1996 ( 25 U.S.C. 4101 et seq. ) or the project sponsor is an Indian tribe (as defined in section 45A(c)(6)), a tribally designated housing entity (as defined in section 4(22) of such Act ( 25 U.S.C. 4103(22) )), or wholly owned or controlled by such an Indian tribe or tribally designated housing entity. (V) Limit on areas designated The portions of metropolitan statistical areas which may be designated for purposes of this subparagraph shall not exceed an aggregate area having 20 percent of the population of such metropolitan statistical areas. A comparable rule shall apply to nonmetropolitan areas. (iv) Special rules and definitions For purposes of this subparagraph— (I) population shall be determined on the basis of the most recent decennial census for which data are available, (II) area median gross income shall be determined in accordance with subsection (g)(4), (III) the term metropolitan statistical area has the same meaning as when used in section 143(k)(2)(B), and (IV) the term nonmetropolitan area means any county (or portion thereof) which is not within a metropolitan statistical area. (v) Buildings designated by State Housing Credit Agency Any building which is designated by