So, what is 'fair'? A new study claims that how we define fairness changes as we age.
Young children like all things to be equal, but older adolescents are more likely to consider merit when it comes to dividing up wealth, said the researchers.
As part of a research study in experimental economics in Norway, 500 school children had to work and then decide how to share their earnings.
The experiment studied both their willingness to share fairly and their perception of what is a fair distribution of income.
Researchers found that the shift from the "egalitarian" view of fairness to the more merit-based "meritocratic" view occurred largely between fifth and seventh grade.
However, it continued to change through high school, with seniors placing the most importance on achievement.
This transition likely results both from changes in the brain as it develops, and from exposure to new social experiences as we age, said the researchers.
For instance, children might participate in more and more activities in which a greater emphasis is placed on individual achievement as they grow up.
A better understanding of what people think is fair, and how this perception develops, might lead to changes in how institutions, such as schools, are set up, said study researcher Ingvild Almas, of the Norwegian School of Economics and Business Administration in Bergen, Norway.
"The idea that social experiences contribute to shape our views on fairness is fundamental to how we design optimal policies and institutions in society such as the educational system," Live Science quoted Almas as saying.
For example, schools might not give academic grades to children when they are very young if grades based on merit do not fit with the fairness views of the children, said Almas.
Previous work has shown that most adults think some inequalities are OK when it comes to divvying up income.
For instance, they think that differences in what people have accomplished can justify an unequal split of money. Or a less than even distribution might be OK if it means the total income for everyone is larger.
However, adults don't agree on whether differences in luck are an OK source of inequalities.
The researchers wanted to know when exactly these views on fairness develop.
They recruited 486 children from 20 schools in Norway in grades 5 through 13. The children played two different games designed to tease out exactly what goes into deciding what is considered fair.
The researchers looked for three types of views on fairness-egalitarianism (those who believe all inequalities are not fair), meritocratism (those who think inequalities regarding differences in achievement are OK) and libertarianism (those who think that all inequalities are OK).
Almas said that the older children's views on fairness match up quite well with those of adults, making the researchers more confident that they actually have captured the progression of these views as people age.
Like adults, older children give more weight to achievements and less to luck when it comes to deciding how to divide up money.
The results will be published in the journal Science.