It worked, so it became the benchmark for long-term prudent investing with some volatility control. Subsequent academic and other work (Modern Portfolio Theory, Bengen's squence of returns risk analysis, etc.) kept showing that 60/40 was approximately the centroid of the efficient frontier of optimizing returns and volatility (typically somewhere between 40% and 75% equities).
In the financial sector, once something works it becomes a religious mantra until it is thoroughly disproven. Even then something can still have legs unless it drove everybody doing it into bankruptcy, in which case it takes 20 years for it to come back in vogue.
60/40 will likely still be going strong a decade from now because it will have proven to be less bad than many of the alternatives.
Re: 60/40 fund - it has actually been around for about a century: https://web.archive.org/web/20190815172840/http:/www.vanguard.com/bogle_site/sp2004wellingtonbth.html
It worked, so it became the benchmark for long-term prudent investing with some volatility control. Subsequent academic and other work (Modern Portfolio Theory, Bengen's squence of returns risk analysis, etc.) kept showing that 60/40 was approximately the centroid of the efficient frontier of optimizing returns and volatility (typically somewhere between 40% and 75% equities).
In the financial sector, once something works it becomes a religious mantra until it is thoroughly disproven. Even then something can still have legs unless it drove everybody doing it into bankruptcy, in which case it takes 20 years for it to come back in vogue.
60/40 will likely still be going strong a decade from now because it will have proven to be less bad than many of the alternatives.