  We present solar low-degree rotational splitting values based on a new
analysis of Sun-as-a-star observations from the Birmingham Solar Oscillations
Network, covering a 16,425-day period from 1976 December 31--2021 December 20
with a duty cycle of 57 per cent. The splitting values are estimated from the
power spectrum using a Markov Chain Monte Carlo sampling method, and we also
present for comparison the results from an analysis of 100 realizations of
synthetic data with the same resolution and gap structure. Comparison of the
scatter in the results from the synthetic realizations with their estimated
uncertainties suggests that for this data set the formal uncertainty estimates
are about 30 per cent too small. An upward bias in the splittings at
frequencies above 2200 microHz, where the components are not fully resolved, is
seen in both the observed and synthetic data. When this bias is taken into
account our results are consistent with a frequency-independent synodic
rotational splitting value of 400 nHz.
