As of the census of 2000, there were 8,967 people, 4,178 households, and 2,272 families residing in the village. The population density was 3,447.8 people per square mile. There were 4,504 housing units at an average density of 1,731.8 per square mile. The racial makeup of the village was 84.63% White, 2.42% African American, 0.04% Native American, 10.01% Asian, 0.04% Pacific Islander, 1.16% from other races, and 1.68% from two or more races. Hispanic or Latino of any race were 4.26% of the population. There were 4,178 households out of which 21.0% had children under the age of 18 living with them, 45.0% were married couplesliving together, 7.4% had a female householder with no husband present, and 45.6% were non-families. 40.3% of all households were made up of individuals and 12.5% had someone living alone who was 65 years of age or older. The average household size was 2.11 and the average family size was 2.92. In the village, the population was spread out with 18.1% under the age of 18, 6.1% from 18 to 24, 29.2% from 25 to 44, 27.6% from 45 to 64, and 19.0% who were 65 years of age or older. The median age was 43 years. For every 100 females, there were 84.6 males. For every 100 females age 18 and over, there were 81.6 males. The median income for a household in the village was $56,725, and the median income for a family was $76,100. Males had a median income of $51,588 versus $43,042 for females. The per capita income for the village was $37,715. About 1.6% of families and 2.0% of the population were below the poverty line, including 1.2% of those under age 18 and 2.5% of those age 65 or over.
In September 2018, the Illinois Department of Public Health began a cancer incidence study based on the recommendation of the Agency for Toxic Substances and Disease Registry. The Willowbrook area shows a '300 in a million' cancer risk based on the 2014 National Air Toxics Assessment, far higher than neighboring communities with a '40 in a million' cancer incidence. A local facility, Sterigenics International, Inc., uses a 'probable carcinogen' called Ethylene Oxide to sterilize medical equipment. According to the EPA fact sheet, 'Long-term exposure to ethylene oxide can irritate the eyes, skin, nose, throat, and lungs, and harm the brain and nervous system. Studies show that breathing air containing elevated ethylene oxide levels over many years increases the risk of some types of cancers, including cancers of the white blood cells ; and breast cancer in females.' On September 30, 2019 Sterigenics announced the closing of the Willowbrook facility eliminating key source of cancer causing chemical.
