"steeper decline" is correct and usable in written English.
You can use it to refer to a dramatic decrease in something. For example, "The stock market had seen a steeper decline this year than in years past."
Analysts had expected a steeper decline of 4.8%.
Facing a steeper decline, publishers are feeling very vulnerable.
A steeper decline in home prices is exacerbating the problems.
The 0th-order (aimpoint) region of the detector shows a slightly steeper decline.
The stock declined 2.5percentt on Tuesday, a steeper decline than the broader Nasdaq.
No other country participating in Pisa saw a steeper decline than Sweden over that period".
Manufacturing output fell by 37 percent, a steeper decline than in 1929-33.
Economists had been predicting a steeper decline, and stock prices rose after the markets opened.
The use of marijuana in that age group showed a steeper decline than overall drug use, declining by 26percentt.
The Midwest, which produces more graduates than the Northeast in any given year, will face an even steeper decline.
The shift reflects a relatively steeper decline in the growth rate in cities, rather than an increase in suburban growth.
