According to World Vision, access to safe drinking water is the most important factor in determining a country's HDI. Unfortunately for Tanzania, 24.6 million people, or half of its population, don't have access to clean water. This results in many airborne diseases such as cholera and and typhoid. On top of this, the poor water sanitation takes out 1-2.5% of Tanzania's GDP every year. When water is not available on the premises of a family home, it is often young girls and women who are sent to collect the water, which takes out valuable time from the education of these young girls. All of these effects of unclean water, including its detrimental health implications, effects on the economy and the impacts on education (especially of young girls) give Tanzania its low HDI, which ranks it as being considered a developing country.