Complex sentence: In 1972, around 450.000 rabbits were used for experiments in the United States, decreasing to around 240.000 in 2006, following the general trend of less animals being used for experiments during especially the last ten years.
Split into simpler sentences: In 1972, around 450 000 rabbits were used for experiments in the United States, decreasing to around 240 000 in 2006. This followed the general trend of fewer animals being used for experiments-especially during the last ten years.