There's not one specifically that I can talk to, but depending on particular risk factors with the country of origin of the applicant, then that could very well result in a higher refusal rate. Again, it depends. Instances of fraud.... From the intelligence that we have available, whether it be previous refusals or just general factors within the applicant's country, with the applicant applying, say, for a student visa to undertake English, but who may not necessarily be a genuine temporary entrant because they're just trying to get out of their own country, could result in a higher refusal rate.
On February 1st, 2017. See this statement in context.