The phrase "a steady decline of" is correct and usable in written English.
It can be used to describe a consistent and gradual decrease in something over time.
Example: "The report indicated a steady decline of sales over the past three years."
Alternatives: "a gradual decrease in" or "a consistent drop in".
The last 20 years of his life he died in 1951 saw a steady decline of his powers.
Since the twenties, there's been a steady decline of other child-care providers, such as household servants and parents and kin.
We have seen a steady decline of drug use in our country over the past two years – it would be a shame to see that reversed.
Economic depression between World Wars I and II, followed by a steady decline of the traditional heavy industries, demonstrated the need for diversification.
Throughout the year Stoiber's stance resulted in a steady decline of support and heavy criticism within the CSU, and he resigned as promised.
PAGE G3 WHERE THE DESIGNERS BUY Despite a steady decline of garment worker jobs in New York, some of the best designers in the world depend on Pat & Rose Dresses, on West 37th Street.
After a steady decline, reports of shootings in the 40th Precinct have also risen, to 46 in 2005, from 31 the year before.
Our specialty is in a steady decline, much of it our own making, and we don't need to help it along by ignoring this obvious issue of integrity.
The dip in the growth of consumers' spending echoed a steady decline in measures of their confidence in the economy.
It's worth noting that nationally, 2014 saw the fewest executions since 1994, part of a steady decline since the peak of 98 executions in 1999.
The relevance of scheduled newscasts, morning newspapers and weekly news magazines is in a steady decline, forcing all of us to experiment with new methods and platforms.
