How are the $DJUSxx industry indexes calculated?

I have never found an answer that I trust on this subject. At EarningsBeats, we use the industry groups as a starting point for "areas" that we like or dislike. They're not ETFs and cannot be traded, so understanding the composition isn't a high priority for us. 

One thing I'll do, however, to compensate if I question which index a stock belongs in, is use the correlation coefficient to determine how closely correlated a particular stock is with an index. As an example, Costco (COST) is included in "personal products" ($DJUSCM) on StockCharts. However, I would put it in Specialty Retail ($DJUSRS). When I pull up the correlation, both are similar.

When I set my default chart on StockCharts, this is one reason why I set up each stock relative to the benchmark S&P 500, as well as its assigned industry group.

-Tom Bowley, Chief Market Strategist