Automotive recall activity in the U.S. remained elevated throughout the first half of the year as the number of recall events fell while the number of affected vehicles jumped.

Tracking recalls issued by the National Highway Traffic Safety Administration, data provider Sedgwick reports that sector recalls were down about 7% year-over-year in the first half. But the number of recalled units surged 112% for a five-year high.

The recall events decline amounted to a six-year low, but some recalls taking in large numbers of vehicles meant many more units requiring remedies.

As has been typical in recent periods, electrical systems led all causes, requiring 74 recalls in the first six months of the year. But that was down 23% from a year earlier. Equipment issues were a close second as the cause of 66 recalls, up 6% year-over-year. Structural problems trailed at a distant third with 26 recalls.

Electrical systems were also behind the biggest number of affected vehicles at 6.2 million recalled units, including one recall of 4.4 million units due to a trailer communication glitch, Sedgwick reported.

A common culprit, back-over prevention systems ranked second for number of recalled units at three million affected. Powertrain problems affected the third highest number of units at 2.4 million, including one recall of 1.4 million units over a transmission issue potentially causing sudden downshifts.