Complex sentence: By 1986, roughly 25% of households in the U.S. owned a microwave oven, up from only about 1% in 1971; the U.S. Bureau of Labor Statistics reported that over 90% of American households owned a microwave oven in 1997.
Split into simpler sentences: By 1986, roughly 25% of households in the U.S. owned a microwave oven, up from only about 1% in 1971. The U.S. Bureau of Labor Statistics reported that over 90% of American households owned a microwave oven in 1997.