Complex sentence: The approval of both houses is necessary for legislation and, thus, the Senate can reject bills passed by the commons: between 1867 and 1987, the Senate rejected fewer than two bills per year, but, has increased in more recent years.
Split into simpler sentences: The approval of both chambers is necessary for legislation and, thus, the Senate can reject bills passed by the Commons. Between 1867 and 1987, the Senate rejected fewer than two bills per year, but this has increased in more recent years.