In July, Baltimore had 45 murders. This was a single-month tally that this city hadn't seen in 43 years ago in 1972.
However, in 1972, the population of Baltimore was over 900,000. Today, the city has a third less people. This means that, this July, the murder rate was 7.5 murders per 100,000 residents. 43 years ago, the murder rate per 100,000 residents was only 5.
Thus, July's killings are statistically higher by 50% than what was seen in one month in 1972.
Baltimore killings soar to a level unseen in 43 years: http://bigstory.ap.org/article/60352506f481415c8edf3fc35b6f8103/baltimore-killings-soar-level-unseen-43-years
Population history of Baltimore from 1790 - 1990: http://physics.bu.edu/~redner/projects/population/cities/baltimore.html
Baltimore's Population 1970 To 2013: https://www.google.com/search?q=baltimore+population&ie=utf-8&oe=utf-8