def tract_id_equals(tract_id, geo_id):
    """
    Determines if a 11-digit GEOID (from the US census files) refers to the same place as a six-digit Chicago census
    tract ID.

    :param tract_id: A 6-digit Chicago census tract ID (i.e., '821402')
    :param geo_id: An 11-digit GEOID from the US Census "Gazetteer" files (i.e., '17031821402')
    :return: True if equivalent, False otherwise
    """
    return geo_id.startswith("1703") and tract_id == geo_id[-6:]