ExxonMobil reported a big drop in fourth-quarter earnings Tuesday, as low oil and natural prices continued to weigh on results.

Net income in the fourth-quarter plunged 39.6 percent to $1.7 billion, while full year earnings fell by more than half to $7.8 billion. Results also were marred by a $2 billion asset downgrade due to low prices, much of it due to impairments in a natural gas region in the Rocky Mountains in the middle of the United States.