Sharp decline: A dozen people were booked into the Ada County Jail on New Year’s Eve on charges of driving under the influence. That is fewer than half of the 29 who were arrested last year.

What are the numbers? Boise made five arrests; Ada County deputies and Meridian police made three apiece; and one unidentified law enforcement agency made one.

Why the drop? Warnings about arrests for drunken driving might finally be getting through to people, some law enforcement officials say. But New Year’s is also a time when people make plans to celebrate and know that police will be out in force, said Tracy Basterrechea, Meridian deputy chief. That makes it a time when they plan for safer ways to get home, he said.