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 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 that the retirement of doctors often only occurs gradually and that their retirement age is increasing (Pong, 2011). The rising share of female doctors may affect the overall supply of medical 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. The growing imbalance in favour of greater specialisation over general medicine raises concerns in many countries about access to primary care for all the population.