administrative levels. Rather they only serve to make city planning, statistics-gathering and other administrative tasks easier and more convenient. Classification Income classification Cities are classified according to average annual income of the city based on the previous four calendar years. Effective July 28, 2008, the thresholds for the income classes for cities are: Legal classification The Local Government Code of 1991 (Republic Act No. 7160) classifies all cities into one of three legal categories: Highly urbanized cities (HUC): Cities with a minimum population of two hundred thousand (200,000) inhabitants, as certified by the Philippine Statistics Authority, and with the latest annual income of at least fifty million pesos (50,000,000 or USD 1,000,000) based on 1991 constant prices, as certified by the city treasurer. There are currently 33 highly urbanized cities in the Philippines, 16 of which are located in Metro Manila. Independent component cities (ICC): Cities of this type have charters that explicitly prohibit their residents from voting for provincial officials. All five of them are considered independent from the province in which they are geographically located: Cotabato, Dagupan, Naga (Camarines Sur), Ormoc, and Santiago. Component cities (CC): Cities which do not meet the preceding requirements are deemed part of the province in which they are geographically located. If a component city is located along the boundaries of two or more provinces, it shall be considered part of the province of which it used to be a municipality. All but five of the remaining cities are considered component cities. Independent cities There are 38 independent cities in the Philippines, all of which are classified as either "Highly urbanized" or "Independent component" cities. A city classified as such: does not have its Sangguniang Panlungsod legislation subject to review by any province's Sangguniang Panlalawigan; does not share tax revenue with any province; and is directly supervised by the President of the Philippines through the city government (given that the provincial government no longer exercises supervision over city officials), as stated in Section 29 of the Local Government Code. Currently, there are only four independent cities in two classes that can still participate in the election of provincial officials (governor, vice governor, and Sangguniang Panlalawigan members): Cities declared highly urbanized between 1987 and 1992, whose charters (as amended) explicitly permitted residents to both vote and run for elective positions in the provincial government, and therefore allowed by Section 452-c of the Local Government