The average family in Ibadan, one of Nigeria's largest cities, spends nearly half its income not on food, rent, or school fees — but on surviving a broken infrastructure system. Buying water from street vendors costs them ten times more than if their home was serviced with piped water. Running a generator to make up for frequent power outages eats further into their budget. Paying unregulated minibus fares to get around drives up their costs even more. Across the continent, this is not unusual. According to the World Bank Group's Africa's Cities: Opening Doors to the World report, African urban households pay 20 to 31% more for goods and services than city dwellers in other developing countries due to their cities’ lack of dense spatial form and infrastructure connections. Missing infrastructure is a regressive tax, driving up poor households’ costs and affecting businesses’ productivity and growth. Therein lies the opportunity: building that missing infrastructure, cleanly, is one of the most powerful ways to make urban life more affordable in developing economies. This would help make cities greener and to reduce their emissions — while also creating more and better jobs for Africa’s growing urban population. Modeling the Path to Green, Affordable Cities This is where the World Bank Group's APEX platform can help. Developed by a team at the International Finance Corporation, APEX — Advanced Practices for Environmental Excellence in Cities — is a data-driven tool that supports city planners to model their environmental footprint, simulate the impact of green investments, and estimate costs and emissions reductions. Using APEX insights, cities can develop “Green City Action Plans” to map out and sequence investments across energy, water, transport, and waste. In Nigerian cities, for example, APEX analysis shows that building clean infrastructure could help households to increase their savings from 0%