Which country is best for children? Not the United States, study finds.

The United States has the largest economy in the world, but its children aren't reaping the benefits, according to a new report.

On Friday, the non-profit Save The Children released its annual "Child Prosperity Index" report, which evaluates 19 developed nations on a number of criteria to determine whether they are good environments for raising children. Despite being the wealthiest country, the United States ranked ninth, trailing behind Germany, Canada, and Italy, among others. 

The report, entitled “Economic Playgrounds 2016” takes into account eight different factors: health, education, income, safety, employment, gender equality, infrastructure, and environment. The index uses indicators such as life expectancy, child obesity, homicide rates, access to water, and air pollution, among many others, to determine the rankings.

The report includes report cards for all countries participating in the G20 summit in Hangzhou, China this fall, where world leaders will discuss world economic cooperation and global development. The ranking excluded only the European Union, which is counted in the G20 as a single overall economy even though several EU member countries are included as well.

According to the Global Wealth Report by Allianz, an international financial service company, the United States is the world’s wealthiest country, controlling 41.6 percent of global wealth. Still, the US is ranked just fifth in the “Income” category according to Save the Children. Though the US has the highest gross domestic product per capita among the G20 countries, it also has one of the highest rates of income inequality, which can have a negative impact on the lives of children.

The Gini index, a measure of income inequality, places countries on a scale of zero to one, with zero meaning a country is completely equal in income, and one indicating the highest disparity in income.  The United States has a Gini index of 0.4, one of the highest among developed nations, according to Fortune. That disparity widened even further in 2015. The average income of the top one percent of US earners grew by 7.7 percent last year, much faster than the four percent growth of the bottom 99 percent.

"Economic growth alone isn't enough to improve the lives of children, there are other things countries need to focus on," Mat Tinkler, the director of policy and public affairs at Save the Children Australia, told USA Today, 

Within the United States, 22 percent of all children live in poverty, according to the National Center for Children in Poverty. Save the Children encourages the tackling of income inequality in an effort to aid in the growth of all children. Vice president of Save the Children USA, told USA Today, "The U.S. really needs to make sure every child benefits from the economic growth of the country.”

The US had its highest category ranking in "Income" at fifth place, but underperformed in areas of of gender equality, health, safety, and environment. The United States performed worst in the “Environment” category because the country is a major emitter of CO2, along with Saudi Arabia, Australia, and Canada.

Germany led the Child Prosperity Index, followed by France, Japan, and Australia. Germany ranked number one for gender equality and employment, as well as in income because of relatively low income inequality within the country.

To help improve their standings, Save the Children advocates for G20 countries to adopt progressive national tax systems that would benefit the poorest citizens, deliver on Sustainable Development Goals (a set of sustainability goals the United Nations developed and countries hope to achieve by 2030), and hold each other accountable, especially when it comes to income inequality.