From available DOJ stats, nearly 30% of all homicides (all causes) in 2005 were committed in:
Birmingham, Phoenix, LA County, LA City, Chicago, Indianapolis, NOLA, Baltimore, Prince George County MD, Detroit, Kansas City MO, St Louis MO, Las Vega, NYC, Cleveland, Columbus, Philidelphia, Memphis, Dallas, Houston and Milwaukee (chosen because of the available data they were all the ones with 100+ murders in 2005)
These cities and counties only contain about 8.5% of our population. If a few other large urban areas were available, I would bet that the differntials would be even greater.
That means, excluding those areas, the rest of the country has a murder rate of about 4.4 /100,000 (calculated) whereas with those areas the murder rate is 5.8/100,000 (DOJ) for 2005, the lowest since 1966. But without those few areas, without that 8.5% of the population, the murder rate is as low as it was last in about 1909. In other words, 91.5% of our population has a murder rate not seen nationally for 100 years. Just 10 years ago, the gap was even larger.
Wisconsin as an example:
Milwaukee contains about 11% of all of Wisconsin's population
In 2005 over 62% of all murders in WI occurred in Milwaukee.
Chicago contains about 22.5% of all Illinois' population.
In 2005 over 58% of all murders in IL occurred in Chicago.
And, since this is the PA state forum:
Philidelphia contains about 12% of all PA's population.
In 2005 nearly 50% of all murders in PA occurred in Philidelphia
How does this apply to this thread? Well, the fact is that a very small percentage of our population can't all live together in a crowded area and those population centers attempt to punish the other 90% of us who generally get along pretty well by restricting our rights over their failures to govern, police and function.
ETA: In various sources the homicide rates reported can vary quite a bit. My data was culled from the DOJ data. Wikipedia, UN and other sources have different numbers. A wiki article on the subject quotes DOJ crime stats as the source but differs by .4 from the DOJ site.