That is true. However, there is a second filtering process, after filtering by experts; and that is what I will refer to as filtering by experiment (i.e. we'll try this, and if it works we keep doing it, and if it doesn't we don't). Evolution is basically a mix of random mutation and filtering by experiment, and it shows that, given enough time, such a filter can be astonishingly effective. (That time can be drastically reduced by adding another filter - such as filtering-by-experts - before the filtering-by-experiment step)

The one-to-two percent expectation that I had was a subconscious expectation of the comparison of the effectiveness of the filtering-by-experts in comparison to the filtering-by-experiment over time. Investigating my reasoning more thoroughly, I think that what I had failed to appreciate is probably that there really hasn't been enough time for filtering-by-experiment to have as drastic an effect as I'd assumed; societies change enough over time that what was a good idea a thousand years ago is probably not going to be a good idea now. (Added to this, it likely takes more than a month to see whether such a social program actually is effective or not; so there hasn't really been time for all that many consecutive experiments, and there hasn't really been a properly designed worldwide experimental test model, either).

That's only true of the programs which can be expected to produce no detriments, surely?