Revamping the district stock index
The composition and methodology of the Ninth District Mid-Cap Stock Index changed at the beginning of April 2013.
In terms of composition, four companies were removed from the index as they relocated their headquarters outside the district or their market capitalization exceeded the maximum threshold for the index. Five new companies were added to the index, expanding the diversity of industries represented as well as geographical coverage. Details on these changes and a current list of companies in the index are available here: Ninth District Mid-Cap Stock Index.
In terms of methodology, the index is now more closely aligned with calculations used in the benchmark S&P MidCap 400 index. Conceptually the district index, like other market-capitalization-based indexes, such as the S&P MidCap 400 and S&P 500, represents the total value of underlying companies normalized to a base year. The rate of change in the index therefore represents the rate of change in the total value of companies included. Under the previous methodology, price changes had a stronger weight and tended to overestimate growth.
As shown in the chart below, the Ninth District Mid-Cap Stock Index moves closely with the benchmark S&P Midcap 400 index. District mid-cap companies appear to have weathered the financial crisis better than the national average; the cumulative growth rate since February 2008 was about 8 percentage points higher than the S&P 400 index. For more details on the Ninth District Mid-Cap Stock Index, see the index methodology.