We often think of efficiency gains in terms of an increase of a few percent here or there. Finessing at the edges. That is not the topic of this book. Rather, it is about making phenomenal strides to make the world better. This book shows us where we can spend money to do the most good, whether we are looking at aid money, philanthropic donations, or funds from developing country budgets.

What this book reveals is that the best polices are hundreds of percent better than an average policy, and the difference between the best and the poorest is thousands of percent.

As will be shown in the Conclusion, it is possible for us to do four times more good with every dollar, euro, or peso spent on development. This is not just about abstract efficiency: it means we can save four people from dying instead of one. It means we can help four children out of poverty instead of one, clean the air for four families instead of one, or teach four girls instead of one.

Being efficient isn't just an arcane concept. It is the difference between leaving the world better and making it four times better.

The UN Global Goals

In 2015, the United Nations negotiated one of the world's most powerful policy documents. Over 15 years, it will influence more than $2.5 trillion of development aid along with trillions from national budgets. It is aimed at helping pull hundreds of millions of people out of poverty, reduce hunger and disease, improve the environment, target the causes of violence, and improve education. Much depends on this being done well.

Tremendous progress has already been made in the fight against humanity's biggest challenges. In 1820 – nearly 200 years ago – around 94 percent of the planet was impoverished. Even in 1990, poverty sat around 52 percent. Recently, the World Bank has found that for the first time ever, in 2015, less than 10 percent of the globe is living in absolute poverty.