Save the Children has published a new report called 'Born Equal: How reducing inequality could give our children a better future', coinciding with a high-level UN panel meeting in London until 2 November to decide new approaches to eradicate global poverty and establish new post-2015 Millennium Development Goals (MDGs).
The MDGs are a story of success. But they have also served to highlight some of the world's most persistent challenges, most notably the scourge of inequality.
When national averages on poverty reduction, hunger, child mortality or education are aggregated between the rich and poor, urban and rural areas, ethnic groups, or by gender or disability, we can see that some individuals and some groups are lagging a long way behind.
Inequality is deeply rooted in countries' history, politics and governance. It can manifest itself in lack of access to services, resources, power, voice and agency.
And it can have costly and disastrous consequences.
Children born into the richest households have access to 35 times the resources of the poorest. These children have better healthcare, more nutritious food and better access to school, and are less likely to have to start work at an early age.
But this is not just a story about income. For many children around the world, being born a girl, disabled, or a member of a minority ethnic group, or growing up in a rural province, also limits your opportunities.
Inequalities such as these are an injustice and an infringement of human rights. We need to place inequality front and centre of the new international development framework - to stem the tide of rising inequalities and to give every child a better start in life.
Addressing inequality will be crucial to accelerate progress towards achieving the MDGs but reducing inequality is an important objective in its own right that should be reflected as a goal in any post 2015 framework.
The world and, in particular, the distribution of poverty within the world have fundamentally changed in the last two decades. In 1990, the vast majority - 93% - of people in poverty in the world lived in low-income countries. Today, more than 70% of the world's poorest people - up to a billion - live in middle-income countries.
The challenge in these countries is not just high levels of absolute poverty - which in many cases has seen astonishing rates of decline - but also relative poverty. The top deciles of their populations are enjoying rapid wealth accumulation, with the resultant effect that there are vast gulfs emerging between rich and poor.
Alleviating absolute poverty in these countries is increasingly a question of how to share the benefits of growth more effectively and minimise the growing gaps between rich and poor. In addition, increasing evidence shows that reducing inequality presents an opportunity to boost economic growth.
According to the IMF, recent evidence "tilt[s] the balance towards the notion that attention to inequality can bring significant longer-run benefits for growth."
Closing these gaps will be crucial to accelerate progress to finish the job we started with the MDGs in 2000 and eradicate global poverty.
While the international community must continue addressing inequalities between countries, addressing gross and increasing inequalities within countries will be one of the most effective and powerful strategies to meet international development goals.
An equitable approach that focuses on addressing the challenges of the world's poorest people has the potential to avert around 60% per cent more under-five deaths for every $1 million invested in public healthcare for children than the current strategies.
A more or less equal world in the years to come will either make or break the prospects of every child to have an equal chance to survive and thrive.