You asked

Almost every FOI request I have seen misses the 20 day time limit. What percentage of requests are handled in the stated 20 days time limit?

We said

Many thanks for your request.

Freedom of Information statistics are published by the Cabinet Office on a quarterly basis, for the Office of National Statistics and other government departments. They are available online here: https://www.gov.uk/government/collections/government-foi-statistics

As this information is already available to you via this route ONS considers that S21(1) applies to this request and the information does not have to be supplied under the terms of the Freedom of Information Act. S21(1) is an absolute exemption and no consideration of the public interest test needs to be applied.