Complex sentence: Cuba exported more than 20,000 metric tons of coffee beans per year in the mid 1950s, and by the 21st century, 92% of the country's coffee was grown in area of the Sierra Maestra mountains.
Split into simpler sentences: Cuba exported more than 20,000 metric tons of coffee beans per year in the mid 1950s. By the 21st century, 92 percent of the country's coffee was grown in area of the Sierra Maestra mountains.