"increase by about" is a correct and commonly used phrase in written English.
Example sentence: The company's profits are expected to increase by about 10% next quarter.
However, the Institute's overall debt load will only increase by about $69 million, because the 2008 and 2009 bonds will now come off its balance sheet.
What's interesting since PSX came out we've seen average size executions increase by about 35%.
Increasing the channel length to 50 nm resulted in the drain current to increase by about 6.6 mA.
It would increase by about 4.5% a year until expiration of the tax in 1989-90.
These numbers continue to increase by about 4%% annually.
A. It's an increase, by about 20 to 25 percent.
Average annual earnings would increase by about $2,800 per year.
He has seen his crop yield increase by about 30percentt.
Average annual earnings would increase by about $2,700 per year.
He estimated that the number would increase by about 33percentthis yearar.
The Open University is forecasting that its numbers will increase by about 10% this year".
