that makes indexing odds quite poor at beating those managed funds.
... for that year that's already passed. The point ERD is making, and I agree, is that your chances of guessing which funds may or may not beat the benchmark each year get less and less as you try to do it year after year (or period after period). Last year, you had an 80% chance of picking a large cap managed fund that beat the index, but that percentage changes every year, certainly many years being significantly less.
So first, you have to pick the sector (large cap, small cap, int'l, etc.) that will out perform, THEN you have to pick a fund that will outperform. And then you have to repeat it.
When you start to factor the odds of getting that choice right all or most of the time, coupled with the head start you get due to exceptionally low expenses with indexing, I'll take indexing every time. Recall that part of the benefit of indexing is the "set it and forget it" ability with your portfolio. Certainly if you're desperately seeking index-beating returns, indexing isn't for you, but most indexers are satisfied with above average returns, low expenses, small tax obligations from dividends, and ease of use.
(Note: "average" is not defined by the index, IMO.)
Either way, one should be planning with a number (i.e. 6% pre-inflation return, or 3% real return, etc.) rather than saying "assuming S&P returns" or "assuming 1% over S&P returns." How you get there... well, that's up to the individual!