Assumptions for Early Retirement

I recently was talking to a friend who disagreed with my retirement planning assumption that our investments would average an 8% return. I had felt that my assumption was conservative given that I am close to 100% invested in equities. He felt that 4-5% was a better long-term assumption. Dave Ramsey assumes 12%. Who is right?

At the end the day, who really knows? We’re doing our best to save and invest a good chunk of our income and staying invested in the asset class with the best track record and best potential growth. But the conversation did get me thinking so I did some additional research.

Over at Moneychimp.com, there is a great resource that shows annual returns on the S&P 500 going back to 1871. You can look at any date range and see returns adjusted for inflation. This is great data for us because the majority of our portfolio is in index funds that track the S&P500. Their biggest takeaway is that:

“Over the very long run, the stock market has had an inflation-adjusted annualized return rate of between six and seven percent.”

When I assume 8% return, I’m assuming that to be before inflation. Is that what my friend meant? I don’t think so, but I’ll have to follow up. My impression was that he was just particularly pessimistic.

I was curious though, so I did some digging into the data set and found some things worth sharing (all numbers not adjusted for inflation).

S&P 500 Historical Returns

  • The best 1-year return for the S&P 500 was 56.8% (1933)
  • The worst 1-year return was -44.2% (1931)
  • Average annual returns from 1871-2016 were 10.7%

As you would expect, the longer you invest the more likely that you wouldn’t have lost any money.

  • The best 5-year annual return was 29.8% (1924-1928)
  • The worse 5-year annual return was -6.9% (1928-1932)
  • The average 5-year return was 10.7%/yr

It took going out to a 10-year time frame before there were no periods where you would have lost money. Investing in the worst 9-year period of 2000-2008, you would have averaged -1.7% per year.

  • The best 10-year annual return was 21.6% (1949-1958)
  • The worst 10-year annual return was 0.6% (1999-2008)
  • The average 10-year return has been 10.8%/yr

Our Retirement Plan Assumptions

The length of time I’m really interested in is even longer than 10 years. My goal is to have my working years last around 25 years and then to be retired for 40+ years. I’m about 10 years in with another 15 to go.

  • The average 25-year period has been an 11.1% return
  • The best 25-year period was 18.2% (1975-1999)
  • The worst 25-year period was 5.8% (1872-1896) 

We first started saving for retirement in 2006 and average market returns from 2007-2016 have been 8.8%. Our returns have been slightly higher than this, but aren’t as clean to track since we have been continuously investing new money for the past 11 years.

All this to say, we’re assuming 8% returns over the next 15 years and based on what we’ve seen so far and what has happened long before we started investing, we remain comfortable with that assumption.

I should have even more years in retirement than in my career, but my plan assumes a low withdrawal rate, under 4%. In retirement, we won’t be relying on sustained market returns to provide for our lifestyle but will remain invested primarily in equities similar to the strategy outlined in Simple Wealth, Inevitable Wealth.

I’m currently reading Nassim Taleb’s book Antifragile and he makes the very valid point that until the worst of anything happened, it wasn’t actually the worst. Said another way, just because a mountain is the tallest you’ve seen doesn’t mean it’s the tallest in the world. I know that future returns could be worse (or better) than we’ve ever seen before, but planning on an early retirement allows me to have sufficient margin in my plan to compensate for unexpected downturns.

See below for some more info on different investment horizons high, low, and average annual returns for a specific number of years.

What rate of return do you use for your retirement planning assumptions?

2 thoughts on “Assumptions for Early Retirement”

  1. I am with you, I use 8% rate of return for my assumptions, this is my average.
    But frankly speaking I’ve got 3 basic assumptions with 4% 8% and 12%. And for “the minimum” scenario I use 4% data

  2. Good idea to include a ‘good/better/best’ case scenario. There are some good free Monte Carlo simulators out there, but I still like using Excel to supplement so I know exactly what scenario is being run.

Leave a Reply