Crain's uses three data points to measure a market's strength: home sales volume, median prices and time on the market before a home is sold. These lists are based on data for the first six months of 2019. The lists separate each neighborhood's market for houses from its market for attached homes (or condos and townhouses) because that is the way the source data is compiled by the Chicago Association of Realtors. In strong neighborhoods, home prices and the median price of homes sold were up in the first half of the year compared to the same period in 2018, and the number of days a home spent on the market was down. In weak neighborhoods, home prices and the median price of homes sold were down in the first half of the year compared to the same period in 2018, and the number of days a home spent on the market was up.