The murder rate in England and Wales has fallen to its lowest level for 20 years with 651 deaths recorded in the 12 months to November 2009.

The Home Office says this figure represents a drop of 14% in the annual murder rate, with 102 fewer deaths recorded by the police in the year to November than in 2007/08.

Senior Home Office statisticians have speculated that advances in medical science, which have saved the lives of some murder victims, may lay behind the decline, but this is not necessarily borne out by the statistics.

The most popular murder weapon remains the knife or other sharp instrument, such as a broken bottle, with 255 of the 651 deaths analysed the result of a fatal stabbing. This compares with 271 knife murders the year before.

However, the police figures show that the overall level of knife crime has fallen by 12%, with particularly substantial declines in robberies and attacks involving grievous bodily harm, suggesting that it is not improved treatment for victims that is behind the fall in the murder rate.

There is a similar picture in gun crime where the number of murder victims has fallen from 53 to 39 – the lowest number since 1989.

The annual Home Office analysis of the homicide figures shows that babies under the age of 12 months remain the most "at risk" age group, with a murder rate of 27 per million.

The next most likely victim is a male aged 16 to 29, with those aged over 70 at the least risk of being murdered. The overall risk of becoming a murder victim is 12 per million population.

More than two-thirds of murder victims last year were male, with 459 male victims and 192 female. Women were far more likely to be killed by someone they already knew (76%) compared with 50% of male victims.

More than half of murder cases last year were due to a quarrel, a revenge attack or a loss of temper, with only 7% – 45 – happening during a robbery or a burglary. Only 4% are attributed to "irrational acts".

The Home Office says the murder rate in England and Wales is broadly in line with other western European nations at 1.43 per 100,000 population based on what happened between 2005 and 2007 comparisons. This is higher than Germany (0.9 per 100,000) and Italy (1.13) but lower than France at 1.46, Northern Ireland at 1.59 and Scotland at 2.17.

But western European murder rates are still far below the homicide rate in the United States. Although murders in the US have fallen substantially in recent years they are about four times as common as in England at 5.6 per 100,000.

• This article was amended on 22 January 2009. The original said that Murders in the US are five times more common than in England. This has been corrected.