A key component of Poverty Reduction Strategies in developing countries consists in assessing the needs of the population in terms of access to basic services such as education, health care, and basic infrastructure. Using Demographic and Health Surveys from 40 countries, this note shows that the needs for household-level services such as connections to the water and electricity networks is likely to be substantially underestimated if governments do not take into account the impact of the demographic transition towards smaller household sizes apart from the impact of population growth. The basic infrastructure needs stemming from the trend towards smaller household sizes is of an order of magnitude equal to half of the needs from population growth.