Beyond the overall number of doctors, the age and gender composition of the medical workforce and the mix between different categories of doctors also have important implications on the current and future supply of medical services. The ageing of doctors in OECD countries has, for many years, raised concerns that there may not be sufficient new recruits to replace them, although there is evidence in several countries that the retirement of doctors often only occurs gradually and that their retirement age is increasing (Pong, 2011). The rising share of female doctors (the feminisation of medical professions) affects the overall supply of services, as women tend to work fewer hours than men, although it appears that working time preferences are becoming more similar among new generations of men and women doctors (Maiorova, 2007). The growing imbalance in favour of greater specialism over generalist medicine raises concerns in many countries about ensuring adequate access to primary care for all the population.