Only five US states were not affected by the bloody, perpetual series of mass shootings in the country this year, according to a website that tracks gun violence.

As of December 2, 353 mass shootings have killed 462 people in 220 cities, according to the Shooting Tracker website, which counts all events that have killed or wounded at least four people.

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A total of 1,317 people were wounded after adjusting for the latest toll from the last mass shooting, which saw a husband and wife couple kill 14 and wound 22 in San Bernardino, California, the deadliest such tragedy in three years.

If there is no slowdown to this frenetic pace, there will be as many such traumatic deadly events as there are days in the year. Or more.

Hawaii, New Hampshire, North Dakota, West Virginia and Wyoming alone were spared such macabre fate.

Experts debate whether the states were spared thanks to coincidence or if circumstances there make them a haven of peace.

All of them except West Virginia have not seen a single mass shooting since 2013, when the website first began its count based not on official figures but on reports obtained from media reports and other sources.

The outcome owes in part to the relatively low population density in those states, experts say.

Wyoming, home to 584,000 people, is the least populous state, according to 2014 estimates from the US Census.

North Dakota, with 739,500 people, is the fourth least populated state, ranking 47th out of 50 overall by population.

“Naturally, we would expect that states with smaller populations would have fewer mass shootings, on average,” University of Alabama criminologist Adam Lankford said.

The most populous state, California with 38.8 million people, had 25 shootings, the second biggest number this year.

Florida, which counted 27 shootings, the most of any state, has a population of 19.9 million, making it the third most populated state.

Lack of shootings in five states a ‘coincidence’

The five states are also among the most rural. Most lack major cities, except for Hawaii, with Honolulu having a population of about 375,000.

Professor Lankford said people in the four states were less likely to live in cities than those in most other US states.

“This affects their risk and probability of experiencing a mass shooting,” he said.

“Although school and workplace shootings do occur in towns and other rural areas, there are many types of mass shootings that mostly occur in cities, such as mass shootings that arise from gang violence, organised crime, and other criminal activity.”

None of these five states, except for Hawaii, has adopted strict gun control legislation, and it is often easier to own one there than elsewhere in the United States.

Wyoming namely does not regulate the transfer or possession of machine guns and no state permit is required to purchase a rifle, shotgun or handgun.

That earns it an “F” from the San Francisco-based Law Centre to Prevent Gun Violence, an advocacy group. North Dakota and West Virginia also get that lowest possible grade.

New Hampshire fared just a hair better, with a D-.

Hawaii, in contrast, got a B+, because of its license and registration requirements, ban on assault weapons and large capacity ammunition magazines, child access prevention requirements and restriction on openly carrying of handguns and long guns.

There have been numerous shootings in those five states, but always fewer than four victims.

“None of them have done anything innovative or effective to prevent mass shootings, it just happens to be … [a] coincidence,” said Adam Winkler of the UCLA School of Law.