Not enough nutrients is called undernutrition or undernourishment while too much is called overnutrition. Indeed, unemployment, poverty, and undernourishment tended to encourage collaboration. Governments alone cannot end hunger and undernourishment. However, the mortality rate due to undernourishment may be reduced. Thirdly, the FAO statistics do not always reflect short-term undernourishment. Likewise, fetal undernourishment can cause a lifelong impairment of the immune system. Under 2.5% of the population suffer from undernourishment. In 1911, Hans Aron performed the earliest study of growth after periods of undernourishment. South Africa has less than 5% of the population facing undernourishment. Undernourishment at 6.3% in 2014 of population remained nearly unchanged since 2007. Undernourishment is most often due to not enough high-quality food being available to eat.