"Petrol prices have tripled in the past two decades."

http://www.bbc.co.uk/news/uk-politics-15730087

Well what does that mean then?

If you have annual inflation of 7% prices would have quadrupled in that period.

Well, according to this site, the average inflation rate over the last 2 decades has been 2.017045%

The doubling time at that rate is 35 years, so clearly the price of petrol has increased above the rate of inflation.

Yet, as this table shows, as recently as 2009, petrol prices, when adjusted for inflation, were lower than in 1983.

So why 20 years? Well petrol prices were at record cheap levels in 1991 and 1992, according to the table linked above. It was actually cheapest in 1992, but saying "Petrol prices have almost tripled in the last 19 years" would have sounded a bit odd.

Want to make something sound expensive? Compare it to when it was cheapest.

So, allowing for inflation, petrol prices have doubled from the lowest point.

Most of that rise has occurred over the last 2 years. And the demands of Tory MPs and the Motoring lobby cannot be met for that much longer, no matter how strident the calls.

driving lessons in Wallasey?