The advice assumes you're investing in an index fund or something equivalent; the market as a whole, amortized, goes up. Individual companies may be a different story.
That itself assumes that the index measures the full universe of all economic activity.
Innovation and startups are themselves evidence that over long (decades) time scales, this isn't true. When a company in the index falls on hard times and folds, where did its revenues go? Frequently, it's to some startup that was privately held until a couple years ago. By the time it IPOs and gets included in the index, much of the wealth has already been generated, and its inclusion in the index is a transfer of wealth from passive investors to the founders, angels, and VCs who funded it when it was far from a sure bet.
A similar situation would occur if a younger generation decides that stocks in general are a scam and that they're going to put all their money into cryptocurrencies. I've met 20-somethings who actually say that; if enough of them believe it, it becomes a self-fulfilling prophecy, and all the old folks whose retirements are in indexed 401(k)s end up holding the bag as those investments become worthless and a younger generation ends up inventing a whole new financial system.
> all the old folks whose retirements are in indexed 401(k)s end up holding the bag as those investments become worthless and a younger generation ends up inventing a whole new financial system
If the world's investments cease to be made in actual companies, in favor of a meaningless commodity, we'll have much bigger problems.
All currency is a meaningless commodity. What matters is how it modulates the flow of real goods and services. A wad of cash is meaningless except as a claim to a share of someone's future productivity, after all.
It creates value for other Bitcoin investors, some of whom might cash out or directly spend crypto building a business. In principle, Joe's Can Factory could be funded by 100 bitcoin which Joe acquired years ago, and the social fads which drove up the price directly enable that.
Of course, right now, the only thing practical to fund with cryptocurrency is a cryptocurrency or internet business, none of which provide truly useful or necessary services
> I've met 20-somethings who actually say that; if enough of them believe it, it becomes a self-fulfilling prophecy, and all the old folks whose retirements are in indexed 401(k)s end up holding the bag as those investments become worthless and a younger generation ends up inventing a whole new financial system.
This is not a problem. If cryptocurrencies become widely used and the associated business accumulate significant market value, major market indices will rebalance in such a way to include cryptocurrency businesses and the passive index investor will be fine.
In fact, it doesn't matter if the future is in crypto, plastic or tulips; equity index investors will be fine.
The mechanism by which the major market indices will rebalance to include cryptocurrency (or any other new form of major economic activity) is that they will sell large amounts of equities at the current price supported by non-index buyers, and they will buy large amounts of cryptocurrency at the price demanded by non-index sellers. That price functions as a large transfer of wealth from index buyers to non-index sellers who bet right on their particular investment thesis. Future price gains (after rebalancing) require that future investors continue to demand more of the indexed securities than other non-indexed securities.
Basically, the index fund itself becomes a bet that the future will look much like the present, at least qualitatively, and that future investors will demand the same categories of securities as present ones do. If the future looks dramatically different from the present, then people who bet correctly with their particular version of the future reap the spoils, at the expense of all index fund investors.
(I should note that this is explicitly the purpose of indexing - by giving up the possibility of above-market returns and settling for market returns, you can eliminate the need for fees. If you believe that being average is good enough, this is a good bet. If you believe that the average person is going to get screwed and bad financial things will happen to the lots of people, why would you want to be them?)
> they will sell large amounts of equities ... and they will buy large amounts of cryptocurrency
More likely they will buy new crypto focused companies (Coinbase IPO) or that existing firms will adopt crypto based business lines. The investment is firms innovating, rather than the value of the underlying instruments or technology they use.
That's entirely possible too, but the problem (for index fund shareholders) is identical if the securities involved are "private preferred stock" rather than "tokens on the Ethereum blockchain". They're still growth opportunities outside the indexed universe that siphon from value opportunities inside the indexed universe, which the index fund can only legally purchase once much of the growth has already occurred.
Index funds strike me as a very bad idea. They reward unprofitable ventures just for being in some index. Buying into an index fund, therefore, is buying into a class of systemically overpriced assets. Yes, backtested, index fund investment does well---but that's because you're backtesting into an era before everyone was bleating "buy index ETFs!".
Between weird investment strategies, the length of the current boom, and the very low interest rates at the peak of the boom, this coming bust is going to be a massacre. I'm honestly not even sure whether the system as a whole will survive it.
