The Dark Knight - [spoilers ahead, ye be warned]

[Alex]

There are various methods used by various sites in trying to create an "adjusted for inflation" index on box office grosses and they all have their flaws.

For what you're describing you'd essentially want to create an index that combines ticket price inflation relative to raw dollar inflation (for example, if ticket prices doubles during a period of 20% dollar inflation then tickets have become more expensive relative to the dollar). And maybe taking into account the overall proportion of entertainment expenses in the average person's accounts.

But generally I'd say that attempting such precision generally isn't worth the amount of time ti would take to do because the of the uncertainties built into the variables. For movies much older than the 1980s we don't really have anything like detailed accounting of box office. Up until WWII movie pricing was much more variable so it is harder to estimate how many tickets a given gross (even if it is well established) would mean. Plus, prior to the wide adoption of VHS significant rereleases of movies were common (particularly by Disney) making these calculations necessary for subsections of the totals.

Which is probably one of the big reasons when people talk box office records they don't usually worry about it too much. Any number will have their flaws.

And yeah, the general decline in gross ticket sales is well established. But that makes a modern anomaly all the more interesting. Based on Box Office Mojos estimates of total ticket sales, only one movie from the last 25 years (1/4 of cinematic history) is in the top 18.