Lowest inflation may refer to years with the greatest deflation or the lowest amount of inflation above or equal to 0%. There were several years before the introduction of the consumer price index (CPI) in 1913 when inflation estimates were reported as 0% largely due to a lack of available data. The highest year-over-year deflation rate before 1913 was in 1780 when it was estimated at 19.34%. The lowest inflation rate above 0% before 1913 was in 1827 when it was estimated to have been 0.83%. As of 2014, the highest deflation rate in 1913 and after was 10.68% in 1921. The lowest inflation rate in 1913 and after was 0% in 1929. Year-over-year inflation is calculated by subtracting the value of the CPI at the end of the year from the value of the CPI at the beginning of the year.