Fewer Americans are giving to charitable organizations than they used to, according to numbers compiled over the past 15 years.

Indiana University’s Lilly Family School of Philanthropy has followed the giving of more than 9,000 individuals and families. In 2005, Americans gave an average of $1,024 a year. As of 2015, the number was $872 per person.

Una Osili is associate dean for research at the Lilly School, and she’s here to go inside the numbers.