Now the drop in the conviction rate can be due to two things:
1) A growing number of people who did commit a sexual offence are being charged and wrongly found to be not guilty
2) A growing number of people who did not commit a sexual offence are being charged and rightfully found to be not guilty
Both situations are not satisfactory. It is extremely repugnant if any rapist gets off.
But it is also repugnant if innocent people are being charged, because the Police now prosecute regardless of the strength of the complaint.
Sadly, I doubt one will ever know whether situation (1) or (2) is more common.