Whenever there’s a strike, the workers’ union and the management fight through the media for public support. The union present arguments concluding that the workers are being treated unfairly, the management present arguments justifying their actions, and both sets of arguments are widely reported. So although strikes are a bad thing for those directly involved, at least they result in some vigorous debate in the press.

At the moment we’re in the middle of a Royal Mail strike. The workers’ complaints are many, but one is (rather predictably) that they aren’t getting paid enough. To support this claim, the Communication Workers’ Union (CWU) has pointed out that postal workers are paid less than the national average. They insist that pay should rise to the national average within five years.

What hasn’t been explained is what relevance the national average salary has to postal workers’ salaries.

The national average salary is derived from data about people in a wide variety of jobs (e.g. cleaners, sales assistants, doctors, lawyers). What’s more, the national average salary is affected by the distribution of workers in these jobs; an increase in the number of doctors, for example, would (other things being equal) increase the national average salary, whereas an increase in the number of cleaners would decrease it.

So why should we think that looking at the national average salary is a good way of decide how much postal workers should be paid? If we knew how postal workers’ hours, skills, working conditions, scarcity, and other factors affecting fair levels of pay compared to the national average, then we might be able to learn something from the comparison, but the CWU hasn’t gone into that. All they’ve given us to support their pay claim is a statistic of very questionable relevance.

The Royal Mail management have used a different statistic to imply that postal workers’ pay is good: Royal Mail postal workers earn 25% more than those who work for other companies in the sector. Whether that’s true or not, I don’t know, but I haven’t heard the CWU dispute it. Whether the Royal Mail figure is accurate or not, if we’re going to decide how much Royal Mail postal workers should be paid based on a comparison to other workers, a comparison to other postal workers seems much more useful than a comparison to the nation as a whole.

Today, Ryanair has threatened to sue the government over the security measures that have recently been imposed at airports. Since a plot to detonate bombs on planes traveling from the UK to the US was uncovered a few weeks ago, air passengers have faced tight restrictions on what hand-luggage they are allowed to carry, and stricter checks than were previously in place when boarding.

The measures have made air travel from the UK extremely difficult. Passengers have endured long delays, and many flights have had to be cancelled, negatively affecting airlines. A Ryanair spokesperson argued that the measures are unnecessary, and said that unless they were lifted Ryanair would be seeking compensation from the government for imposing them.

To support this claim that the security measures are unnecessary, the spokesman made a comparison with the 7/7 Tube bombings. After the bombings, he pointed out, the government got the Tube service back to normal within a matter of days. There is therefore no reason, he inferred, for the current security measures at airports to continue weeks after the plot to bomb aircraft was uncovered; things should be back to normal by now.

This argument overlooks important differences between the two cases; it draws a weak analogy. For example, the Tube bombings did not involve the discovery of any new threat, and so once the damage done had been repaired and the crime scene examined, things could return to normal. The discovery of the recent terrorist plot, however, raised a new danger: the possible use of liquid explosives. It therefore required new security measures to be introduced indefinitely.

This difference between the cases that the Ryanair spokesman compared means that the comparison can’t support the conclusion that he drew from it.