The United Kingdom Society for Women in Philosophy and the British Philosophical Association Committee for Women in Philosophy conducted a survey of philosophy departments between 2008 and 2011. There were 38 departments that responded to the survey. The survey covered data on undergraduate students, doctoral students and staff. This survey suggests that there is significant leakage of women from the philosophy discipline in the UK. Women were particularly well represented in Senior Lecturer positions, with 28 per cent of the total staff being women, however women represented a mere 19 per cent of professorial positions. There is also an important variation between the proportion of women in temporary staff positions, estimated at 28 per cent, and the proportion of women in permanent positions estimated at 24 per cent. Women leave at various points of the philosophy pipeline. While women represented close to one in two of undergraduate students, they were less that one in three of PhD students, at 31 per cent (Beebee & Saul, 2011).
Figure 1. Distribution of academic appointments in philosophy, UK, by position and gender, 2008-11

Source: Beebee & Saul (2011), p. 9.
The AdvanceHE Report for 2018 gives the female proportion of academic staff in Philosophy as an increase to 29.7 per cent. The underlying data from the Equity Challenge Unit shows that 23.7 per cent of professorial appointments are women (an increase from the Society for Women data), and 31 per cent of all other appointments are women.
Figure 2. Proportion of women in philosophy at professor/not professor level, 2018

Source: Underlying HESA data used by Advance HE, Equality + higher education: Staff statistical report 2018, available at Advance HE website, accessed January 2019.
Reference
AdvanceHE (2018) Equality + Higher Education Staff Statistical Report.
Helen Beebee and Jenny Saul. (2011). Women in Philosophy in the UK, A report by the British Philosophical Association and the Society for Women in Philosophy UK Joint BPA/SWIP Committee for Women in Philosophy