The data on occupation were derived from answers to Questions 44 and 45. Written responses to the occupation questions are coded using the occupational classification system developed for the 2000 census and modified in 2002. This system consists of 509 specific occupational categories, for employed people, including military, arranged into 23 major occupational groups. This classification was developed based on the Standard Occupational Classification (SOC) Manual: 2000, published by the Executive Office of the President, Office of Management and Budget. Some occupation groups are related closely to certain industries. Operators of transportation equipment, farm operators and workers, and healthcare providers account for major portions of their respective industries of transportation, agriculture, and health care. However, the industry categories include people in other occupations. For example, people employed in agriculture include truck drivers and bookkeepers; people employed in the transportation industry include mechanics, freight handlers, and payroll clerks; and people employed in the health care profession include janitors, security guards, and secretaries.