SmartETF

Testing Forward Looking Asset Allocation

Can we finally kill Modern Portfolio Theory? How much pain does one need? If it worked why are all of your accounts so decimated? Why is Meriwether on the verge of another Long-Term Capital explosion and where are your 10% annualized returns?

Flaw #1: MPT relies on normal distribution which by defaults ignores risk outside of 3 standard deviations (sigma 1=68.3%, sigma 2=95.4%, sigma 3=99.7%), or .15% for each tail. So what are the odds of a 5 sigma event? It’s one in 7000 years. So tell me why have we had a half dozen 5 sigma events or more this year? The use of normal distribution is simply wrong. Changing to a log-based distribution called a ‘stable distribution’ exposes the tails to better see risk.

Flaw #2: MPT uses linear correlation. This static approach illustrates the average relationship of 2 assets over time. This is crazy because as Geoff Considene accurately points out the relationships change (becoming more correlated) as volatility increases. The old adage is the only thing that goes up in down markets is correlation. So why not use a dynamic correlation model that adjusts for volatility. It exists and it’s called a ‘copula dependency model’.

Flaw 3: MPT is based on long-term averages. If in 2000 you used 40 years of history to model equities returns you would expect returns of 10%. Using 15 years you would return 15%, using 3 years you would model 30%. So the key in most models is know how much data to use and how best to weight the data. The author here is weighting new data as being more valuable; which is actually true. The danger in doing this however is during cycle changes (like 2000) and it disregards historical patterns. So exponentially weighting may be better than mean-variance but EWMA’s have its main flaw is its inability to appreciate historical data (patterns like a 60’s or 70’s market) because it works like a present value model that heavily discounts old data.

Using a physics concept called GARCH takes the historical data and examines its recent clustering effect; think Doppler radar instead of MVO’s Farmer’s almanac approach. The GARCH concept won its inventors the Nobel Prize in Economics in 2003, a bit more recent than the MPT concept developed 50 years ago.

Flaw #4: Rebalancing more than once a year is considered inefficient to the MPT user; which is true. That is because new data is meaningless. Adding a month of new data into a data set of 40 years is like throwing a bucket of water into a pond; meaningless. This is why asset allocators always hold fast to their 60/40 mix range. If you could value newer data as more valuable you would rebalance more often to capitalize on the change in market conditions (risk & return). This is why the QPP model is trumping MVO/MPT because it rebalances more than the buy & hold and it ostensible values newer information as more valuable.

The bottom line is MVO models just don’t work except in long up-trending markets, but you’ll never outperform. Mandelbrot, Sharpe and several of the other inventors of MPT/CAPM express their issues about their creation and yet these words go unheeded because it is in the text books and accreditation programs. Mandelbrot recommends Extreme Value Theory (EVT), a dynamic approach to asset allocation. Using EVT for the past four years you would have had nearly twice the returns of the basic 60/40 mix in the up years and been down only half that amount this year. That is serious alpha. So let’s bury MPT/CAPM and these mean-variance models and take a scientific approach to investing.