Per capita annual GDP for several countries (Austria, Canada, France, Germany, Greece, Italy, Sweden, UK, and USA) during 1950-1983. One interest lies in studying the "periodic" behaviour of such series in connection with understanding business cycles. Another lies in forecasting turning points. Another lies in comparisons of characteristics of the series across national economies. Notice the GDP of Greece soar from the 60s until the end of 70s. Source: Department of Statistical Science, Duke University, 2015