The researchers analyzed data from 14,000 families. For participants followed from 1991. The researchers compared the level of family income with the number of night probujdeni children. Experts have found a close correlation between the time parents spent the night to calm the child, and loss of income.

By the way, earlier researchers from the University of Warwick found that children around the world cry different amounts of time. Thus, in the first three months of life most children cry in Britain, Canada, Italy, the Netherlands and several other countries. But in Denmark, Germany and Japan, the children cry less.