Question: what is the population of the area where Tom Purtzer was born?

full_context: Document 1: Matt Peterson: Peterson was born in Chicago, Illinois. He played college golf at the University of Georgia where he won one event and was a three-time All-American. He turned professional in 1990.
Document 2: Scott Radecic: Graduating from Brentwood High School in 1980, he played college football at Penn State University, where he was an Academic All-American in 1982. His brother Keith also played at Penn State and in the NFL for the St. Louis Cardinals in 1987.
Document 3: Richard Tufts: Born in Medford, Massachusetts, he was a grandson of James Walker Tufts, the founder of Pinehurst Resort in North Carolina, which was long America's preeminent golf resort. Richard Tufts grew up in Massachusetts and attended Harvard. He served in World War I before starting work at Pinehurst with his father Leonard, and later taking over himself. He added 40 holes to the resort and hosted the 1936 PGA Championship and the 1951 Ryder Cup. He ran Pinehurst until relatives sold their stock to Diamondhead Corp., ending family control.
Document 4: Findlay S. Douglas: Born in St Andrews, Scotland, Douglas learned to play golf as a boy. He attended the University of St Andrews from 1892 to 1896, and played on the golf team. After graduation, he followed his oldest brother Robert and emigrated to the United States in 1897.
Document 5: Des Moines metropolitan area: The Des Moines metropolitan area, officially known as the Des Moines -- West Des Moines, IA Metropolitan Statistical Area (MSA), consists of five counties in central Iowa, United States: Polk, Dallas, Warren, Madison, and Guthrie. The 2010 census population of these counties was 569,633, and the 2017 estimated population was 645,911.
Document 6: Frank Walsh (golfer): Walsh was born in Chicago, Illinois. A number of his brothers were professional golfers including his elder brother, Tom, who was president of the PGA of America in 1940 and 1941.
Document 7: Des Moines, Iowa: Age spread: 24.8% under the age of 18, 10.6% from 18 to 24, 31.8% from 25 to 44, 20.4% from 45 to 64, and 12.4% who were 65 years of age or older. The median age was 34 years. For every 100 females, there were 93.8 males. For every 100 females age 18 and over, there were 90.5 males.
Document 8: Indianola, Iowa: Indianola is a city in Warren County, Iowa, United States, 18 miles south of Des Moines, Iowa. The population was 14,782 at the 2010 census. It is the county seat of Warren County.
Document 9: Johnston, Iowa: Johnston is a city in Polk County, Iowa, United States. The population was 17,278 in the 2010 census, an increase of almost 100% from the 8,649 population in the 2000 census. It is part of the Des Moines–West Des Moines Metropolitan Statistical Area.
Document 10: Des Moines, Iowa: On September 22, 1851, Des Moines was incorporated as a city; the charter was approved by voters on October 18. In 1857, the name ``Fort Des Moines ''was shortened to`` Des Moines'', and it was designated as the second state capital, previously at Iowa City. Growth was slow during the Civil War period, but the city exploded in size and importance after a railroad link was completed in 1866.
Document 11: Saylorville, Iowa: Saylorville is a census-designated place (CDP) in Polk County, Iowa, United States. The population was 3,301 at the 2010 census. It is part of the Des Moines–West Des Moines Metropolitan Statistical Area. The Saydel Community School District is located in this area. The unincorporated community of Marquisville is in this area.
Document 12: Tom Purtzer: Purtzer was born in Des Moines, Iowa. He attended Arizona State University in Tempe, where he was a member of the school's golf team. He graduated in 1973 and turned pro. He followed in the footsteps of his older brother, Paul, who also played golf for Arizona State and played on the PGA Tour in the 1970s and early 1980s.
Document 13: Middletown, Iowa: Middletown is a city in Des Moines County, Iowa, United States. The population was 318 at the 2010 census. It is part of the Burlington, IA–IL Micropolitan Statistical Area.
Document 14: Mike Nicolette: Nicolette was born in Pittsburgh, Pennsylvania. He attended Rollins College in Winter Park, Florida and was a member of the golf team. While a student at Rollins, he won the 1976 NCAA Division II Men's Golf Championship. He turned pro in 1978.
Document 15: Cedar Rapids, Iowa: As of the 2010 United States Census, the city population was 126,326. The estimated population of the three - county Metropolitan Statistical Area, which includes the nearby cities of Marion and Hiawatha, was 255,452 in 2008. Cedar Rapids is an economic hub of the state, located in the core of the Interstate 380.
ground_truth: 645,911
sub_queries: Tom Purtzer >> place of birth Answer: Des Moines
what is the population of the Des Moines area Answer: 645,911