Sales of $4.6 billion in the fourth quarter of 2018 were down 1% compared to the year-ago period. Changes in foreign currency exchange rates reduced sales by 4%. Organic sales increased 3%, as net selling prices improved 3%. Organic sales declined 1% in the year-ago period. In North America, organic sales increased 6% in K-C Professional, and 3% in consumer products compared to a 3% decline in the base period. Outside North America, organic sales rose 4% in developing and emerging markets and were even year-on-year in developed markets.
In the personal care segment, fourth quarter sales of $2.2 billion decreased 2%. Changes in currency rates reduced sales by 5%. Net selling prices increased approximately 2%, volumes rose 1% and product mix improved slightly. Fourth quarter operating profit of $436 million decreased 11%. The comparison was impacted by input cost inflation, unfavorable currency effects and increased marketing, research and general spending, while results benefited from cost savings and organic sales growth.
Sales in North America increased 4% due to higher volumes. Volumes were up mid-single digits in the infant and child care mega category, driven by growth in Pull-Ups training pants and GoodNites youth pants. Volumes were also up mid-single digits in adult care, led by Depend products.
Sales in developing and emerging markets decreased 9%. Currency rates were unfavorable by 12%, primarily in Latin America. Net selling prices rose 5% and product mix improved 1%, while volumes fell 3%. The higher net selling prices were primarily in Latin America and secondarily in the Middle East/Eastern Europe/Africa, partially offset by decreases in China. The lower volumes included declines in China and Argentina, and increases in ASEAN and Eastern Europe.
Sales in developed markets outside North America (Australia, South Korea and Western/Central Europe) decreased 4%, including a 3 point negative impact from changes in currency rates. Net selling prices fell approximately 2%.