Just realized something pretty interesting about Buffett's whole index fund philosophy. So everyone knows he's crushed it with stock picking — averaging like 20% annually since the 60s — but what's wild is that he basically tells everyone else to forget about it and just throw money into the S&P 500 instead.

Here's the thing though: if you actually look at what happens when you save 100 a week for a year and keep it rolling, the math gets pretty compelling. Index funds are just baskets of stocks grouped by common characteristics, and the value moves as the overall index moves. Vanguard, Fidelity, these companies created them so regular people could actually invest in entire market segments without needing a fortune.

Buffett's obsessed with the S&P 500 specifically — it's 500 of the biggest US companies across different industries, basically a snapshot of the whole economy. The reason he pushes it so hard? Lower risk because you're diversified across hundreds of companies, not betting on one stock. Plus the fees are way lower than actively managed funds where fund managers are constantly trading and charging you for the privilege. You know exactly what you own, and historically these broad-market funds just keep delivering around 10% average returns year after year.

Let me break down what $100 weekly actually looks like over time. After 10 years of contributing 52k, you'd have around 87k total with the returns. Jump to 20 years and you're looking at over 312k. Thirty years? Nearly 900k. Forty years? We're talking 2.4 million. That's compound interest doing the heavy lifting.

If you started at 20 and invested that 100 every week until 65, you'd retire with almost 4 million in the account, even though you only actually contributed like 166k yourself. The returns dwarf your contributions after enough time passes.

One caveat though: the S&P isn't equally weighted anymore. The top 10 companies now represent almost 30% of the index value — mostly tech giants like Apple, Microsoft, Nvidia. So if the tech sector sneezes, the whole index feels it more than it used to. Some people prefer equal-weight S&P 500 funds to avoid this concentration risk, but honestly, talk to a financial advisor about what makes sense for your situation.