Iowa’s seasonally adjusted unemployment rate fell to 2.8 percent for December, compared with 3.5 percent a year ago. The U.S. rate remained at 4.1 percent. “Iowa businesses finished 2017 strong, bolstering payrolls by 7,100 jobs in December. Iowa factories added 11,700 jobs in 2017,” Beth Townsend, Iowa Workforce Development director, said in a statement. But she said the low unemployment presents a challenge. “With an unemployment rate at 2.8 percent, Iowa must address the shortage in skilled workers. It will take all hands on deck to sustain this economic growth.” The number of working Iowans increased to 1,637,800 in December. That was 200 more than November and 3,200 more than one year ago.