Fill in the gap: “Sales increased ___ five per cent this year.”

Many Dutch people are led astray here by the fact that the equivalent verb in Dutch takes met (‘with’). However, the correct preposition to use with verbs like increase, rise, grow, reduce, cut, slash, lower, fall, decline, extend, lengthen or shorten to indicate ‘how much’ is by:

We have slashed prices by 25 per cent!
Official Development Assistance has declined by one-third.
The number of internet users is growing by leaps and bounds.
The roofline has been lowered by 34mm to 1390mm.
The gap between rich and poor widened by EUR 243 a week last year.
Annual asthma-related costs have been reduced by more than EUR 13,000.  

©2015 Baxter Publishing, Hilversum, The Netherlands