On the use of percentages by the hundred

A percentage is a simple thing : a salary increment of one and a half percent, a three percent cut in the unemployment figure, are within everyone’s comprehension. And yet, even practiced journalists and the proofreaders who check on them may easily get mixed up. Here are two examples within the past year :

In La Croix (a French national daily paper) dated Tuesday July 6, 1999, Bruno Chenu, in a paper under the title “football’s millions”, writes : “The transfers that have gone on this month are dizzying. In four years, the size of transactions has been multiplied by four. 400 % inflation : that’s not bad !”

Dizzying... and give you hallucinations, if you take plus 400 %, which means a multiplication by five, for a multiplication by four. Plus 100 % means doubling, and plus 200 % is therefore a tripling, etc...

Be this as it may, such magnitudes definitely are frightening, and as the author of the paper says : “How can we get out of this spiraling inflation, which should, after all, end up shocking ordinary spectators and reasonable supporters ?”.

Sub-zero standard of living

More recently, in Télérama (a cultural and TV program magazine) dated December 29, 1999, Gérard Chaliand, a specialist in geo-strategy, was questioned on the outcome of the December 1999 legislative elections in Russia. He interpreted the results as “the symptom of a disoriented population”, and added : “How would we react if we had lost something like 300 to 400 % of our standard of living in less than five years ?”. As we know, the temperature is often sub-zero in Russia, but we were unaware that the same could be true of the standard of living !

Blunders of this sort may be avoided by using percentages properly, which is to say when the variations they are supposed to measure are small. A percentage of 100 % or more is difficult to comprehend. Beyond 100, it is best to speak of doubling, tripling, etc. Similarly, for large drops, it is preferable to speak of halving, instead of a 50 % drop, or a division by 3, rather than a drop of 66.6666666... %.

That’s easy to say, however. Take prices : a price rise is normally expressed in percentage form, since prices are supposed to change slowly, but there can always be inflation, which may reach 8,000 % for instance. So, dear reader, what would you say the multiplier would be, here ? 

Alfred Dittgen
June 2000

Penumbra, 2001 June