reduce by

reduce something by something

to diminish something by a certain amount. I have to reduce your allowance by two dollars per week until you pay me back for the broken window. I will reduce the bill by a few dollars.
See also: reduce
References in periodicals archive ?
Switching from the use of standard silanes to NXT Low V silane, tire manufacturers can reduce by 70 percent the smog causing ethanol VOC emissions during manufacturing and, in the process, reduce their investment in emission abatement equipment.
By removing all barriers and simplifying the process, Canada Post expect error rate to reduce by 95% (leaving 5% for security access problems).