Effect of savings, investment return and time on retirement

I recently stumbled upon an article discussing the timeline for reaching financial milestones like $100,000, $200,000, $300,000, and so on. This prompted me to contemplate the key determinants shaping our ultimate retirement portfolio value. Three primary factors immediately came to mind: (1) the length of the investment period, (2) the savings or investment rate, and (3) the investment's return rate.

I conceptualize retirement value as akin to the area enclosed by a triangle, where the three factors outlined above serve as the triangle's sides. In an ideal setting, our aspiration is to optimize all three factors to their fullest extent. However, in a pragmatic context, one of these factors must step in to compensate for the shortcomings of the other two, ensuring a well-balanced approach to retirement planning.

In my analysis, I consider one million dollars as a benchmark for a contented retirement. While the adequacy of this sum for retirement can be a topic of debate, it's safe to say that most of us would find having a million dollars to be a highly satisfying prospect. I've set the retirement age at 65, aiming to reach the million-dollar milestone by that age in a worst-case scenario, recognizing that achieving it earlier is even more desirable.

In my calculations to determine returns on a purely stock portfolio, I have utilized the Total Stock Market Index Fund (VTSMX). With an inception date of 4/27/1992, VTSMX has consistently delivered an average annual return of 9.96%. Therefore, an all-stock portfolio is presumed to yield a return of 9.96%.

Likewise, for my all-bond portfolio, I've employed the Total Bond Market Index Fund (VBMFX), which has been in operation since 12/11/1986 and boasts an average annual return of 5.89%. To compute returns on diversified portfolios, I adopt a linear combination of VBMFX and VTSMX. For instance, a portfolio composed of 50% stocks and 50% bonds would exhibit annualized returns of 7.93%.

In the first scenario, let’s say a person starts investing $6,000.00 per year at the age of 22. $6,000.00 per year comes out to be $500.00 per month and should be something an average person can afford to invest. In fact it is very close to the contribution limit for IRA ($5,500). We vary the return on investment from a very conservative portfolio i.e. 100% in bonds to a very aggressive portfolio i.e. 100% in stocks. The power of compounding and time is very obvious from this chart. Even with a very conservative portfolio it is possible to reach a million dollars at an age of 63. The other investment strategies are faster with an all stock portfolio getting us there at age of 51. The thing I like the most about this scenario is we can be totally risk averse and still attain our goals. Since, I did not consider inflation adding stock components should compensate for it.

In the second scenario, let’s say a person still continues to invest $6,000.00 per year. But, instead of starting at the age of 22, we try out multiple start points i.e. 22, 27, 32, 37, 42 and 47. There is not much of a difference between starting at ages 22 and 27. With a ROI of 7% (Conservative portfolio) it is possible to reach our goal of million dollars. Starting at age of 32, we are looking at a very aggressive portfolio to reach our goal. At 42+ even an all stock portfolio is not going to be successful in getting us to our goal. The only alternative is to than increase the contribution (see next chart).

For the third scenario, let’s assume a ROI of 8.75%. This corresponds to an aggressive portfolio with 70% invested in stocks and 30% invested in bonds. Again, instead of starting at the age of 22, we try out multiple start points i.e. 22, 27, 32, 37, 42 and 47. Since, the ROI is fixed the contributions have to increase to help us achieve our goal. It is still possible to achieve our goal by investing 6,000$ per year as long as you start ahead of 32. Starting 37, we need to invest 9,000$ per year to meet our goal. This is because diminishing effect of compounding. It goes all the way up to $23,000 per year at the age of 47. One thing to keep in mind is that wages do increase with work experience. So, even if we miss the boat at a younger age, we could still reach our goal by saving/investing more (thanks to wage increases we might be able to afford it). Catch up contributions to IRAs and 401s provide us this opportunity.

This is a dividend investment blog. Hence, I wanted to finish off with a dividend reinvestment example. For this illustration I am going to use the S&P 500 index. Historical data on S&P 500 index is publicly available on Robert Shiller’s website. The data is quite exhaustive and includes data from 1871(Yes! S&P 500 index is really old). Furthermore, I will be using a 50 year time period i.e. 1967 to 2017. One thing to consider is 500$ was worth a lot more in 1967 (thanks to inflation, debt level etc.). So, in my computation, I computed dollar adjusted values by normalizing with 2017 CPI (consumer price index) value.

Let’s say I have been investing $6,000.0 per year in the S&P 500 index from 1967. The only growth I had in my investment was from dividends reinvestment i.e. dividend yield is my annualized return. How much would by portfolio worth be in 2017? It would be worth $618,373.89. Using the average yield of S&P 500 from 2017 our portfolio would generate $11,986.73 in passive income.

In conclusion investing early and often is a sure shot method to a successful FIRE. We have seen that the most dominating factor is not the amount invested or the investment ROI. The most dominant factor is time. Starting early with a modest monthly investment (let’s say 500$) and investing in a moderately conservative portfolio is a good investment strategy. For someone who has been unable to invest early, contributing a larger amount is a good strategy. It might be possible to take advantage of catch up contributions after age of 50.