Why is it necessary for the University to ask about my sex at birth for registration?

We are required by HESA (Higher Education Statics Agency) to report aggregated data about University of Surrey students. This is a mandatory, statutory requirement for us and in providing this data we allow HESA to fulfil its role in collecting, analysing, and disseminating UK higher education statistics for public benefit, policy formulation, funding, and research.One of the fields we are required to report is ‘Sex’. Students that do not to wish to provide this data are able to do so by selecting the ‘Prefer not to say’ option.