Jag mÄste fÄ bolla en sak som jag har gÄtt och tÀnkt pÄ nu ett tag, men som jag inte riktigt landat Àn. Jag, vi och de flesta brukar ju sÀga saker som att:
- Tiden Àr spararens bÀsta vÀn
- Tiden âjĂ€mnarâ ut den genomsnittliga avkastningen
- Investerar du 0 - 2 Ă„r, bankkonto, 10+ Ă„r, aktier
- etc.
Jag upplever Àven att det Àr mycket som mÄnga - t.ex. fondrobotar och finansiella rÄdgivare bygger sin premiss pÄ. Men pÄ senare tid sÄ har jag sett glimtar av akademiker som inte upplever att det stÀmmer. Nu senast nÀr jag hÄller pÄ med researchen till veckans avsnitt dÀr tvÄ professorer skriver uttryckligen:
Thereâs a common fallacy that you can reduce your risk simply by investing over a longer time horizon. This hokum says that investing $1,000 for each of forty years is less risky than investing $1,000 in each of thirty years. Not so. Both the risk and the reward go up with the increased investment.
NÀr en annan professor, James Choi, intervjuas hos Ben Felix pÄ Rational Reminder sÄ kommer han ocksÄ in pÄ det:
For popular authors, thereâs this really strong sense that stocks become less risky as the investment horizon increases. Actually, if you look at the data, itâs really hard to find evidence that thatâs true. You look at the annualized standard deviation of the S&P 500 in the post-war period, and you just change the holding period from one year to three years, to five years, to 10 years, the annualized standard deviation is pretty flat.
This notion that the stock market mean reverse is just not there very strongly in the data at all. Then, there was this very famous theorem that was independently proven by Nobel Laureates Paul Samuelson and Bob Merton, I think it goes back in the late 60s that they published these papers independently, that shows that if, indeed, stock returns are like that, that they have an annualized standard deviation that doesnât change as the investment horizon increases and more exactly speaking, itâs true that every year the stock return this year doesnât really depend at all on the stock return in the prior year, then your asset allocation optimally should not change as your investment horizon increases, or decreases. Itâs a fairly counterintuitive result, but itâs just standard theoretical result in the finance literature.
Popular authors say, âNo, no, no. Actually, it is the case that the longer you hold the stock, the stock market, the less risky it becomes.â The way they justify this is they say, look, historically, and this is absolutely true. As the length of time you hold the market increases, the likelihood that you are going to underperform the risk-free bond decreases. Voila, you should actually hold more stock as your investment horizon increases.
Now, thatâs taking a fairly simple view of risk, which is the risk hasnât paid off if the stock investment has underperformed the bond investment, which is very intuitive, in fact, and seems to make a lot of sense. The reason economists rejected that criterion is it actually matters by how much you underperform the bond. Itâs not just a 1-0, youâve underperformed or not. As the investment horizon increases, it is true that the likelihood that youâre going to outperform the bond in the stock investment does increase. The worst-case scenario also gets worse and worse and worse, or the worst-case possible scenario gets worse and worse and worse as the investment horizon increases. It turns out that those two forces exactly offset each other. Thatâs the economic theory.
Just to finish up on the popular authors, because they think that stock investments are less risky as time goes on, they say, you should bucket your money according to when you think youâre going to spend it. Any money that youâre going to spend in the near term, and near term could be as long as in the next 10 years, the most extreme, but the median author would say something like, in the next five years. Youâre going to spend that money in the next five years, that should be all in cash. Because stock market is too risky for any money thatâs earmarked for a shorter spending horizon.
Then itâs this money that you donât think youâre going to spend for a long time, thatâs the money that you should think about putting into the stock market. There are some authors that use some variant of the 100 minus age rule. You should have a 100 minus your age percent of your long-term money in the stock market. There are the authors that say that any money that youâre not going to spend in the near term should be invested in the stock market. Itâs a very horizon, or investment horizon-driven advice thatâs out there.
Kan vi inte hjÀlpas Ät att bena ut det hÀr? För jag har en lite obehaglig kÀnsla dÄ jag kÀnner mig lite trÀffad av James Choi i texten ovan⊠
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