BASF, the world's biggest chemicals maker, said Wednesday that its full-year profits came out lower than expected last year due to falling oil prices.BASF said in a statement that underlying or operating profit tumbled by 18 percent to 6.2 billion euros ($6.7 billion) in 2015 on a 5.0-percent decline in revenues to 70.4 billion euros. It put the impairments or writedowns at an estimated 600 million euros, which it would book in the fourth quarter.BASF had previously been expecting to book only "slightly lower" operating profit for 2015 after having already cut its full-year goals at the end of October in face of slowing growth in China and the weaker global economy.