Chicago saw a homicide total lower than 500 in 2019, the first time under that threshold since 2015. The spike in violent crime that has plagued Chicago since 2016 has even more gravity when viewed in comparison with six decades of homicides in Chicago. Since 1957, the city has had homicide totals of 700, 27 of 63 years, and has been lower than 500 a third of the time, 20 of 62 years. To understand this long-term view, the Tribune asked two experts to give perspective as to what was behind Chicago crime decade by decade, and combed through news...