Complex sentence: The success of the stabilization program was attributable to a combination of good luck and good management and the impressive development during this period was referred to as the "Spanish miracle", between 1959 and 1975 Spain had the next fastest economic growth rate after Japan.
Split into simpler sentences: The success of the stabilization program was attributable to a combination of good luck and good management and the impressive development during this period was referred to as the "Spanish miracle". Between 1959 and 1974, Spain had the next fastest economic growth rate after Japan.