I'm sure it's been stated a hundred times already, but since people don't seem to let it sink in I'll say it again. Karen's strategy is directional. It's a bull market strategy. Nobody should be surprised that in the last 5 years, a clearly bullish directional strategy on the SPX would work. Why people like to lump Karen's trading in with direction neutral strategies I have no idea, but it's very disingenuous to do this.
"most consistent publicly available strategy " If this strategy ever exist, all the" public" traders will be millionaire and winner, and not the 90% losers.
Man I am up late so I hope this response makes sense. It is still possible to lose or blow out an account with a backspread. The risk might be easier to manage with a backspread because it is more defined. It is similar to trading a butterfly against a butterfly in the futures market. The backspread mitigates some risk, increases commissions cost, increases bid ask spread cost and decreases profit. A backspread strategy may still erode an account over time.
One last thing...IMHO, a known unknown is easier to manage than unknown unknown. Not trying to be cryptic, just stating an opinion.
What are the listed variance swap instruments? I found this one (but cannot seem to get a daily chart on it ...): http://cfe.cboe.com/Products/Products_VA.aspx
It is based on a quote from Donald Rumsfeld and Nassim Taleb cites it in his book. I think the quote has utility in trading options. For example, a short options strangle has unknown and potentially devastating risk. A wrangle or back spread has limited and defined risk. Pragmatically, it is easier to manage a position where risk is clearly bound (or as bound as risk can be in options trading)...IMHO.
You can't trade them listed. Only through OTC which would require an institutional account with an isda. My statement was more for illustrative purposes.
What is the most statistically predictable Option strategy? They all are predictable. Anyone with a basic understanding of options should be able to predict a rough value of the position depending on the value of the underlining. The underlining is the unpredictable part.
The statistically most predictable option strategy according to your definition is simply a short box (giving a credit and receiving the risk free rate), although this is obvious not the answer you expected to hear.