Reasonable yield rate for life tenant

I use the STEP benchmarking stats they issue for comparisons on investment/capital growth but does anyone know of any similar benchmarking stats to use to assess if the yield for the life tenant is reasonable (and I suppose, by implication with the need to balance the needs of all the beneficiaries, adjacent stats on the capital growth for the remaindermen of a life interest trust) ? Does anyone have any recent figures for what life tenant yields are presently producing for the life tenant.

Many thanks in advance.

Caroline Bates
Davidson Mahon