The idea that the DJIA level is only legitimate if the same companies are used is foolish. The individual companies are weighted and they have constantly been changed to reflect industry.
When the average was first introduced it had a number of railroads, Western Union and even leather companies. Would you really want to use those companies today? Do you really think that getting rid of Sears and adding Walmart was a bad idea? Should Studebaker still be on the list?
http://www.quasimodos.com/info/dowhistory.html
Details? Are they weighted the same way as other indexes?
actually more fair to say I think the djia is a public-consumption average, and if a person wants to take a serious look at the state of the blue-chip market they might consider the s&p 100 or 500 depending on min. market cap they consider of interest.
while the dow utilities and transport deal with sectors narrow enough to have some accurate reflection in their indices, djia as an overall market proxy (which is what it is treated as by the general public) is dubious.
inflation is something I think should be taken into account when looking at averages over any period of time if the average is, say, based on a product priced in dollars.