The researchers suspect that greater public awareness may have been, in part, what has helped.

The study found that the percentage of youth receiving unwanted online sexual requests declined from 13 percent in 2005 to 9 percent in 2010. Youth experiencing unwanted pornography exposure declined from 34 percent to 23 percent over the same period.

On the other hand, youth reports of online harassment increased slightly from 2005, up from 9 percent to 11 percent.

“The constant news about Internet dangers may give the impression that all Internet problems have been getting worse for youth but actually that is not the case,” said lead author Lisa Jones, research associate professor of psychology at the UNH Crimes against Children Research Center. “The online environment may be improving.”

Jones pointed out that unwanted sexual solicitations are down more than 50 percent since 2000, when attention first was drawn to the problem.

“The arrests, the publicity and the education may have tamped down the sexual soliciting online” said author Kimberly Mitchell, research assistant professor of psychology at the UNH Crimes against Children Research Center. ”The more effective safety and screening features incorporated into websites and networks may have helped reduce the unwanted encounters with pornography.”

Jones said harassment may not have fallen because attention to that online problem has been more recent. “Hopefully, the new focus on online harassment will produce some of the same improvements in this problem that we have seen in sexual solicitations,” she said.

The authors cautioned that unwanted sexual solicitations should not be understood as necessarily communications from adult online predators. Previous research has found that while youth do not know the source of all the unwanted sexual solicitations they receive, when they did know, half were believed to come from other youth.