LAGOS, Nigeria (AP) The worlds population is projected to hit an estimated 8 billion people on Tuesday, according to a United Nations projection, with much of the growth coming from developing nations in Africa.

Among them is Nigeria, where resources are already stretched to the limit. More than 15 million people in Lagos compete for everything from electricity to light their homes to spots on crowded buses, often for two-hour commutes each way in this sprawling megacity. Some Nigerian children set off for school as early as 5 a.m.

And over the next three decades, the West African nations population is expected to soar even more: from 216 million this year to 375 million, the U.N. says. That will make Nigeria the fourth-most populous country in the world after India, China and the United States.

We are already overstretching what we have the housing, roads, the hospitals, schools. Everything is overstretched, said Gyang Dalyop, an urban planning and development consultant in Nigeria.

The U.N.s Day of 8 Billion milestone Tuesday is more symbolic than precise, officials are careful to note in a wide-ranging report released over the summer that makes some staggering projections.