Take the Total Post Index, it should go up over time. Taking the average of everyone's posts is the best way to go.
Hmmm... Think I'll stick with the WMH-index. Passively tracks only the Walrus + Magnum + Handlebar posters. Sure, you loose out the potential, near-exponential growth of start-up accounts, but since so many of those fail within the first 5 postings I think the sheer volume of the larger posters will make up for it.
Only problem with the WMH is that it's weight-adjusted, so I still feel too heavily exposed to 'Rebs, thegoblinchief & dragoncar. Posting analysis are already predicting reduced output from 'rebs, so that might be already priced in. Maybe I'll balance it out with some holdings in the foreign bogleheads posters. Still - lot of crossover there too. Hmm...
There's no way the total post index will match inflation. A fulll 33% of users have zero posts. Meanwhile, Rebs is 2.1% of the index. You still have a lot of exposure. BTFD
I'm still surprised, even after my warning people to read the prospectus, the rumor persists that rebs is included in the WMH index, to the point that dragoncar thinks nereo is overweight in rebes, when actually he has zero exposure.
And forum posts are hardly an efficient market. I have my connection closer to the source, so I can post 0.0001ms faster, thus I can flash post and front run other people's answers. Don't forget that--as a mod--I have access to hidden sections of the forum for insider posting, as well. It's a rigged game.