Question: What is the mean income in Belvedere Island's county?

full_context: Document 1: Tiburon, California: Tiburon is an incorporated town in Marin County, California. It is located on the Tiburon Peninsula, which reaches south into the San Francisco Bay. The smaller city of Belvedere (formerly a separate island) occupies the south-west part of the peninsula and is contiguous with Tiburon. Tiburon is bordered by Corte Madera to the north and Mill Valley to the west, but is otherwise mostly surrounded by the Bay. Besides Belvedere and Tiburon, much of the peninsula is unincorporated, including portions of the north side and the communities of Strawberry and Paradise Cay.
Document 2: Fresno County, California: The median income for a household in the county was $34,725, and the median income for a family was $38,455. Males had a median income of $33,375 versus $26,501 for females. The per capita income for the county was $15,495. About 17.6% of families and 22.9% of the population were below the poverty line, including 31.7% of those under age 18 and 9.9% of those age 65 or over.
Document 3: Homestead Valley, Marin County, California: Homestead Valley is an unincorporated community in Marin County, California. It lies at an elevation of 33 feet (10 m). For census purposes, Homestead Valley is aggregated with Tamalpais Valley into the census-designated place, Tamalpais-Homestead Valley.
Document 4: Lairds Landing, California: Lairds Landing is an unincorporated community in Marin County, California. It is located on the southwest shore of Tomales Bay south of Tomales, at an elevation of 36 feet (11 m).
Document 5: Detroit: Oakland County in Metro Detroit, once rated amongst the wealthiest US counties per household, is no longer shown in the top 25 listing of Forbes magazine. But internal county statistical methods – based on measuring per capita income for counties with more than one million residents – show that Oakland is still within the top 12, slipping from the 4th-most affluent such county in the U.S. in 2004 to 11th-most affluent in 2009. Detroit dominates Wayne County, which has an average household income of about $38,000, compared to Oakland County's $62,000.
Document 6: Lewis County, West Virginia: The median income for a household in the county was $27,066, and the median income for a family was $32,431. Males had a median income of $27,906 versus $18,733 for females. The per capita income for the county was $13,933. 19.90% of the population and 16.30% of families were below the poverty line. 27.00% of those under the age of 18 and 11.20% of those 65 and older were living below the poverty line.
Document 7: Bivalve, California: Bivalve is an unincorporated community in Marin County, California. It is located on the Northwestern Pacific Railroad northwest of Point Reyes Station, at an elevation of 43 feet (13 m).
Document 8: Household income in the United States: One key measure is the real median level, meaning half of households have income above that level and half below, adjusted for inflation. According to the Census, this measure was $59,039 in 2016, a record high. This was the largest two year increase percentage increase on record.
Document 9: Buckingham County, Virginia: The median income for a household in the county was $36,378. Males had a median income of $36,420 versus $32,327 for females. The per capita income for the county was $16,938.  About 21.1% of the population were below the poverty line.
Document 10: List of highest-income counties in the United States: Rank County State Median Household Income Loudoun County Virginia $134,464 Howard County Maryland $120,941 Fairfax County Virginia $115,717 Hunterdon County New Jersey $113,684 5 Santa Clara County California $111,069 6 Arlington County Virginia $110,388 7 Douglas County Colorado $109,292 8 San Mateo County California $108,627 9 Morris County New Jersey $106,985 10 Williamson County Tennessee $106,054 11 Nassau County New York $105,870 12 Somerset County New Jersey $104,478 13 Marin County California $103,845 14 San Francisco County California $103,801 15 Delaware County Ohio $101,693 16 Forsyth County Georgia $100,909 17 Montgomery County Maryland $99,763 18 Calvert County Maryland $98,732 19 Prince William County Virginia $97,986 20 Stafford County Virginia $97,484 21 Putnam County New York $96,992 22 Anne Arundel County Maryland $96,483 23 Charles County Maryland $95,735 24 Rockwall County Texas $95,731 25 Middlesex County Massachusetts $95,249
Document 11: Belvedere Island, California: Belvedere Island is an unincorporated community in Marin County, California. It lies at an elevation of 69 feet (21 m). Belvedere Island is on the part of Belvedere Island (in San Francisco Bay) that is not incorporated in the city of Belvedere.
Document 12: Vincent Landing, California: Vincent Landing (formerly, Vincents Landing) is an unincorporated community in Marin County, California. It is located on the northeast shore of Tomales Bay southwest of Tomales, at an elevation of 20 feet (6 m).
Document 13: Bird Island (Marin County, California): Bird Island is a small island between Point Bonita and Rodeo Cove in southern Marin County, California. It is located off the coast of Marin Headlands, about three miles from San Francisco.
Document 14: Household income in the United States: One key measure is the real median level, meaning half of households have income above that level and half below, adjusted for inflation. According to the Census, this measure was $59,039 in 2016, a record high. This was the largest two year percentage increase on record.
Document 15: Hampshire County, West Virginia: The median income for a household in the county was $31,666, and the median income for a family was $37,616. Males had a median income of $28,884 versus $19,945 for females. The per capita income for the county was $14,851. About 12.90% of families and 16.30% of the population were below the poverty line, including 22.70% of those under age 18 and 13.10% of those age 65 or over.
ground_truth: $103,845
sub_queries: Belvedere Island >> located in the administrative territorial entity Answer: Marin County
what is the average income in Marin County Answer: $103,845