Should ski helmets be compulsory?

The death of Natasha Richardson has sparked a debate about whether it should be mandatory for skiers and snowboarders to wear helmets.

There's been a sharp rise in the number of people wearing helmets after several high-profile ski accidents this winter and some compulsion has already come in.

However, the medical evidence is not conclusive and it's not thought any widespread compulsion is imminent in the Alps.

This winter Lower Austria made it compulsory for all children under 14 to wear a helmet after the death of a 41-year old woman who had a high-speed collision with the German politician, Dieter Althaus, in January. He was wearing a helmet and survived, while she had no head protection.

After the accident, helmet sales increased sharply in Austria and Germany and some shops ran out of stock. In the UK, retailer Snow and Rock reports a 15% growth in sales this winter.

Italy already makes it compulsory for children to wear a helmet and many ski schools across the Alps insist on it.

"Serious head injuries are thankfully comparatively rare in skiing but are a significant cause of death and severe long-term disability," says the consultant surgeon, Jonathan Bell.

"There is good evidence that even moderate head injuries can lead to some permanent disability.

"A helmet will protect against minor injury by absorbing some of the impact and spreading the load, thus possibly reducing the severity of injury."

This winter in Austria seven people have died as a result of collisions on the slopes. In total, 29 skiers and snowboarders have died in ski accidents this season.

So, how many people already wear a helmet?