The study looked at changes in the volatility of 214 US economic indicators from 1959 to 1999. They found that most of these indicators had a change in volatility during this time, with many experiencing a decrease in volatility due to changes in how variable they were over time. The study also found that nominal variables like inflation and interest rates had multiple periods of increased volatility, especially in the 1970s. Overall, the study suggests that economic fluctuations have become more stable over time.