The article looks at why some groups who borrow money together don't pay it back. They used a special math model to figure out what makes a group more likely to not pay back their loan. They found that bigger groups, more women in the group, and more money saved by borrowers make it less likely for the group to not pay back. But if the group borrows a lot of money or has more experienced business owners, they are more likely to not pay back. The article suggests that successful businesses should move on to bigger banks instead of borrowing more from microfinance institutions.