What a $200 Monthly Investment in a Low-Return ETF Looks Like After 25 Years

Here's a thought experiment. Nothing fancy, no options strategies, no crypto, no stock tips. I'm not trying to change your life with incredible returns here. It's just this hypothetical idea: What if you quietly put $200 a month into the most boring fund on the planet, for 25 years straight, and then looked at what you had at the end?

The exchange-traded fund (ETF) I'm thinking of here is the SPDR Bloomberg 1-3 Month T-Bill ETF (NYSEMKT: BIL). This fund makes money market accounts look exciting. It holds short-term Treasury bills, collects a little yield, and hands it back to you. This type of Treasury carries low interest rates even at the best of times, in exchange for ultra-stable market value. The share price has been almost flat throughout BIL's history. It's not trying to make you rich. Instead, it promises to not lose your money.

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So that's the experiment. Start with nothing. Add $200 a month, reinvesting those tiny distributions along the way, for 25 years. Over the past 19 years (since its launch in 2007), BIL has produced an annualized total return of roughly 1.33%. Those modest $200 sums would add up to $60,000 after a quarter-century. Together with the reinvested payouts, you'd end up with about $71,100. The fund made you more than $11,000 by just existing.

Now imagine you started that account the day your kid came home from the hospital , swaddled in those ubiquitous striped receiving blankets. You keep it up through the sleep deprivation, the soccer practices, the rougher teenage years, and college. After grad school, a pile of seriously useful money is sitting there. It's enough for a car, down payment on a house, a robust emergency fund, or a head start on retirement -- built one boring month at a time.

And again: That's BIL. It's the fund equivalent of a concrete bunker. Safe, stable, and uninspiring.

Take that same discipline -- $200 a month, every month, don't stop -- and put it into something like an S&P 500 index fund instead. I'm still talking about really basic ideas like the Vanguard S&P 500 ETF (NYSEMKT: VOO). These funds are not trying to beat the market at all. They just mirror the returns of the S&P 500 (SNPINDEX: ^GSPC) index with minimal fees.