"diminish effectiveness" is correct and usable in written English.
You can use it to refer to a decrease in the power or efficiency of something. For example, "The computer virus quickly diminished the effectiveness of the software program."
Not only does this diminish effectiveness, because they can't improve lessons year on year, but watching thoughtfully crafted lesson plans torn up every September is plain soul-destroying.
For those who care deeply about social problems and work tirelessly to make a difference, current foundation practices not only diminish effectiveness, they inevitably reduce the satisfaction that donors, staff, and trustees derive from their work.
Success is not determined by where we end up, it's about the journey... and failure does not diminish effectiveness, it builds character.
If programs are not financially sustainable, there is a very high risk that they will be disrupted, which would greatly diminish effectiveness.
The diminishing effectiveness of the chemical effect of CO2 dilution with increasing pressure is due to the significant decrease in the H radical mole fraction.
The early-acting beneficial mutations proposed by these theories are maintained in populations despite their subsequent deleterious effects due to the diminishing effectiveness of natural selection as reproductive individuals age (Hamilton 1966; Charlesworth 1980).
While some existing reviews identify brief intervention effects on alcohol problems or composite outcome measures, they also suggest diminished effectiveness among those with more severe problems, as effect sizes are lower if dependent drinkers are not excluded [ 18].
The diminishing effectiveness of nonprofit efforts created an opening for commercial settlement companies.
Here, too, dancers clinging together came unglued again and again, but this time with diminishing effectiveness.
Others who have had similar procedures — most notably Chien-Ming Wang — have faced repeated setbacks and diminished effectiveness.
The diminishing effectiveness of conventional advertising and the rise of social media have led more and more brands to embrace content marketing.
