I was analysing the data provided by Schiller (http://www.econ.yale.edu/~shiller/data.htm). On the first row (year 1871) the value for CPI index is 12.46. Anyone know the source of this value? I thought it was the accumulated CPI index, but i couldn't get this value.Schiller dataset
The answer is in the link you posted... (emphasis mine)
The CPI-U (Consumer Price Index-All Urban Consumers) published by the U.S. Bureau of Labor Statistics begins in 1913; for years before 1913 1 spliced to the CPI Warren and Pearson's price index, by multiplying it by the ratio of the indexes in January 1913. December 1999 and January 2000 values for the CPI-Uare extrapolated. See George F. Warren and Frank A. Pearson, Gold and Prices (New York: John Wiley and Sons, 1935). Data are from their Table 1, pp. 11–14.