Planning for the right balance between all these sources of revenues calls for strategic financial planning, so as to evaluate the potential for mobilising financing from each source of revenues as well as reducing costs. For example, some financial information is available for central government and external donors spending, but information on subnational and local government expenditures is seldom aggregated at a national level. In addition, because funding for sanitation and hygiene is often spread over several different institutions, budget data are less available for sanitation and hygiene than for drinking water. Data on private sector investments (ranging from large private operators, informal providers, households or remittances) is notoriously difficult to collect, although they potentially represent an important source of funding for the sector. Furthermore, selecting cheaper and more locally appropriate investment options or adapting service levels can generate substantial savings and support the definition of more realistic investment programs.