This chart is the Real (inflation adjusted) NASDAQ Composite index. The data in the chart is calculated by multiplying each data point in the NASDAQ - Monthly chart by the ratio of the last and corresponding data point in the U.S. CPI - Monthly chart. A log scale is used to better illustrate the relative size of price changes.
mccormick-charts.com: NASDAQ - Monthly, U.S. CPI - Monthly
Wikipedia: NASDAQ Composite