KPMG conducted an internal audit in order to better understand how pay-gaps between different types of workers relate to socio-economic background, as determined by the jobs held by employees' parents.
The data indicates, maybe unsurprisingly, that the pay gap was greatest between KPMG employees who come from a professional household and those have a working class background, which differed by a little under 9%. The next largest gap was between employees with middle tier backgrounds and employees who originated in the working class, which was a little over 6%. The pay of workers whose parents have a professional background and the pay of workers whose parents had middle tier backgrounds was most similar - separated by only a little over 2% at the median.
KPMG has set a goal in the United Kingdom of having employees with working class backgrounds hold 29% of their partner and director-level positions by the end of this decade.
You can read more about these data analyses and conclusions here.