A lot of portfolio back tests (and their resulting charts) are just silly. Any moron can go into a spreadsheet to find what worked best in the past (especially when cherry picking dates). But it takes some real thinking to work out a strategy that can deal with future unknown risks.
You can't optimize for returns going forward because you don't know what those returns will be. So anyone designing a portfolio based only on what worked best in the past is making a major tactical error with their investments. A mistake that could destroy a retirement plan.
What I liked most about our "Forever" Portfolio is that it eliminates most risk. As a lifelong entrepreneur, I really believe that after 40 years of trading and investing, I understand the nature of the unknown and investing RISK. It's not about going into a spreadsheet, hand picking some dates and blend of assets to see what did best, and then going out and buying those investments. If investing were that easy we'd all be filthy rich!
Rather, back-testing can really only show you what DIDN'T work well in the past, so you can avoid repeating those mistakes, or at least be aware of those risks. Back-testing can never prove something will work best going forward. Also, back-testing will never show you extraordinary events, such as civil unrest, unprecedented government intervention in the markets, inflation, etc.
These risks need to have some diversification applied as well and the Forever Portfolio actually considers these risks that spreadsheet-only portfolios do not.
This is why I find it so absurd when some analyst or pundit claims that an asset like gold is "worthless" in an investing portfolio because of some biased spreadsheet work they did. I wonder if these people have ever gotten far enough away from their spreadsheets to see how the world markets really work?
Having some portfolio insurance like gold around is a really splendid idea. YES, the Forever Portfolio holds gold, silver and displays a good record with other assets likes stocks (mainly ETFs), bonds and cash. But what in history suggests this is not a good idea? Show me the flaw! Show me the data?
It doesn't matter what your chart is showed worked best over a particular time period. The fact is that concentrating your bets is dangerous, and sometimes your stocks and bonds don't payout on your timetable. This is just how life works. I am finding out more each day. Diversifying a little bit is prudent.
Using Charts Intelligently
Investing charts are one tool investors have, but I think they need to be used within their limits. Charts can't predict the future, but maybe they can guide you away from notably bad ideas. Likewise, they can also be useful to test out theories for big flaws you might have missed. Even then, they need to be used with some judgement about the unpredictable future and the idea that history has many ugly details buried within it that aren't simply explained in a chart of spreadsheet data. When looking at investing charts, just keep in mind that pretty colors and compelling growth patterns may not be enough to prevent disaster if you don't use the data intelligently.