4. What Drives the Pay Gap?
A detailed, but now old (2001/02 data) study  estimated the percentage of the ( UK) overall pay gap (full- and part-time workers) associated with different drivers as follows:
- 38% of the overall pay gap was due to 'Other factors associated with being female', including discrimination
- 36% was due to differences in working patterns
- 18% was due to structural labour market differences, and
- 8% was due to educational differences:  .
The largest contributor, 'Other factors associated with being female' includes direct discrimination but also could reflect underlying differences between genders in preferences and motivations towards work and unpaid care. The extent to which direct discrimination, i.e. discrimination on the basis of gender alone, contributes to the pay gap is difficult to determine. However, many of the other factors set out above may be associated with indirect discrimination.
Indirect discrimination can contribute to underutilisation of women's skills. As an example, studies suggest that women in Science, Technology, Engineering and Mathematics careers can often experience systems and structures, policies, processes and procedures that are discriminatory, even where the employers have the very best of intentions on fairness and equality  .
For example, while there is general agreement that appointments should be based on 'merit' and the 'best person for the job', concepts of what constitutes 'merit' are socially constructed and can be influenced by preconceived views of men and women. They can also value some qualities or attributes more than others. Women can be significantly disadvantaged by a gendered conception of merit, for example if it places particular value on a full-time, uninterrupted career trajectory and research success  .
The large contribution to the pay gap of differences in working patterns suggests that higher rates of part‑time work and interruptions to employment tend to reduce women's accumulation of skills and experience.
There is substantial international and UK evidence to suggest that women who return to work after having a child / children are more likely to experience downward mobility. Long term risk of downward mobility in mothers is likely to be particularly affected by the availability of quality part-time opportunities and flexible working opportunities.
KEY MESSAGE: a large proportion of the pay gap is currently un-attributable to characteristics other than 'being female'. This implies that direct, and in particular, indirect discrimination in the way that work is organised continue to play a significant role in driving the pay gap and causing many women to 'downgrade' their employment in order to balance work and caring commitments.