Hamish McRae: Ask before you send: Is this email really necessary?

A survey from law firm Peninsular suggests BlackBerry users spend an extra couple of hours per day doing some form of work. Photo / Greg Bowker

Do you BlackBerry on holiday? Because, if you do, the chances are you are also putting in an extra 15 hours a week when you are back at work.

That conclusion would follow from a survey by Manchester law firm Peninsular, which suggests that if you have a BlackBerry you spend an extra couple of hours a day doing some form of work.

If you really want to be online 24 hours a day, there are many ways of being so.

A huge amount has been written about the social consequences of this revolution, but much less attention has been paid to the economic consequences.

Come back to those extra hours supposedly being worked by BlackBerry addicts. What is happening is not so much that people are working longer, for people who choose to work long hours or are in jobs that require that will always do so. Rather it is that their downtime is being used much more effectively. So it is the moments that would have been wasted, the 10 minutes waiting for a train, that are being used more effectively.

This has huge consequences. There are only a certain number of hours in the day, and only a certain number of people in the workforce. Even if we all go on working into our 70s, the numbers of people available to do the jobs that have to be done will start to shrink in Britain, as they are already shrinking in Japan.

One possible outcome, as is happening in Japan, is falling living standards. One of our weapons against that is to use technology to figure out ways of enabling people to work more efficiently.

All that will continue to develop as both the technology and our competence as users improves. But the greatest gains will come from changes in personal work habits, our competence as producers. The use of downtime is one of the most important of these.

But because the ability to use the spare minutes to bang off a few emails is still so new, we probably use that time badly. It is not just a question of hitting the send button before we have thought through the consequences of our email; we probably send emails that don't need to be sent at all.

That will be the overriding feature of most people's work for the next few years. We have to focus on the quality of output rather than the quantity of input.

One way forward will be for people to use downtime, time that was previously wasted, and that is where the BlackBerry or equivalent comes in. The harder task will be to work out not how to communicate more but rather how to get things done while communicating less. In World War II railway posters asked: "Is your journey really necessary?" Now, maybe it should be: "Is your email really necessary?"

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