According to the BBC, the United States is an outlier when the gun murder rate is compared with the gun murder rates of other highly developed countries.
Some 9,960 people were murdered with a firearm in the USA in 2010, a rate of 3.2 per 100,000 people. . . . when compared with other highly developed countries, the rate shows the US as an outlier.http://www.bbc.co.uk/news/world-us-canada-20759139
The article then goes on to provide the gun murder rates in some other highly developed countries. The gun murder rate per 100,000 in the U.S. is more than 10x the gun murder rates per 100,000 in Norway, Australia, the Netherlands, New Zealand, Germany, Japan, and England+Wales.
Could it be that this is because the these countries have much stricter gun control laws than the United States. For example, in England (where the gun murder rate is .1 per 100,000 people) anyone wanting to own a gun must go through a lengthy process designed to weed out potential applications.
According to another BBC article:
It starts with an application form which asks specific questions about why the individual wants a gun, telling them they need to show "good reason". . . .http://www.bbc.co.uk/news/10220974
Independent referees provide confidential character statements in which they are expected to answer in detail about the applicant's mental state, home life and attitude towards guns.
Officers check the Police National Computer for a criminal record and they speak to the applicant's GP for evidence of alcoholism, drug abuse or signs of personality disorder. Social services can also be asked for reasons to turn down an applicant.
Finally, senior officers must be sure that prospective shotgun holders have a secure location for the weapon, typically a dedicated gun cabinet. Each certificate is valid for five years.