Rob B;329966 wrote:Recency bias (another year of stellar market returns)?
Mostly this.
Retail investors don't evolve – they just adapt their behaviour and philosophy to back-fit recent history.
Historically, large-cap growth has been the worst part of the market to invest in. There was a theory that businesses, like dinosaurs, outgrow their environment. This may still be the case. So even 10 years ago, you had a dozen better places to invest than the S&P: UK micro-caps, quality, perpetual bonds, Asia, etc.
Taking the market return felt like giving up to most on here. "I've done better with this collection of 10 randomly chosen unit trusts – why would I buy the index?"
Indexes traditionally win by always doing about average. Investors are hyper-focused on the past 1-3 years, so they think average is absolutely terrible. Where they fail is always being in the right funds. They can always pick the funds they should've been in over the past few years. And right now, that just happens to be a US or world index – which makes investing appear very simple.