The phrase "discernable effect" means something that can be noticed or understood because it has made a noticeable impact or difference. Full definition
On the corporate side of the code, tax expert Bill Gale and his colleagues summarize that «there is virtually no evidence that broad - based [corporate] tax cuts have had a positive effect on [economic] growth... That has been amply demonstrated at the national level, where tax cuts have eroded revenue without discernable effect on economic activity.» (jaredbernsteinblog.com)
Conclusions: There is no scientifically discernable effect for IP (distant intercessory prayer) as assessed in controlled studies. (religion.blogs.cnn.com)
These are some of the first numbers we've seen that actually measure something that most of us in the digital politics space assume: that online social behavior has discernable effects in the Real World. (epolitics.com)