“cFIREsim stands for Crowdsourced Financial Independence and Retire Early Simulator.

If the market does no worse than the great depression, 1970’s stagflation, or the dotcom bust, will my money last in retirement?

The math behind retirement: The simple question of “Will my money last in retirement?” is rife with complications. Do you have a good handle on what your expenses are? What sort of investments do you have? How long might you live? Do you have any large one-time expenses in the future? What happens if you retire during a major market downturn? What happens if you retire in the worst market downturn in history?

Retirement advisors and various financial websites will often give you the most overused “Rule of thumb” in the financial world. The “4% rule”, derived from the Trinity Study, states that if you have a retirement period of 30 years, you can safely withdraw 4% of your portfolio in year 1 of retirement and continually adjust that for inflation, without fear of running out of money. Critics of this study say that the financial world is a much different place than it was in the past, and that we should adjust our thinking on how much we should withdraw in retirement.

How do I know if my portfolio will last? At it’s most basic level, cFIREsim uses historical stock/bond/gold/inflation data from 1871 to present, and calculates how your portfolio would have fared throughout history. If you enter a 30 year simulation period, it will run your data for every 30yr period in history. Example: cFIREsim will figure out your portfolio value, if you would have theoretically retired for the period of 1871-1900, then for the period of 1872-1901, 1873-1902, etc. It will take all of your inputs and determine whether or not the portfolio “failed” (failure is defined as going below $0 at any given point). What does this tell me? If cFIREsim says that your portfolio survived 95% of the simulation cycles, it means that if the market does no worse than the worst years in recorded stock market history, your portfolio will survive.

What can cFIREsim do? At it’s core, you can enter information in the a few simple inputs and return the basic simulation. At it’s most complicated, it can determine your portfolio success based on 80 individual portfolio adjustments, multiple types of inflation, multiple types of market returns, and graphically show you the results. There are many options to choose from outside of the “Basic Inputs”. You can find information for each section within this FAQ.


Basic Options Calculator

“Our Basic Options Calculator…provides fair values and Greeks of any option using our volatility data and previous trading day prices. You may customize all the input parameters (option style, price of the underlying instrument, strike, expiration, implied volatility, interest rate and dividends data) or enter a stock or options symbol and the database will populate all those fields for you! Note that the option’s underlying price is the previous trading day’s market closing price.

Basic Options Calculator

For those that are new to options, as I am, one of the ways of assessing the option in question is by calculating its delta, which from Investopedia, “represents the [rate of change] between the option’s price and a $1 change in the underlying asset’s price”. Crucially, however, what the delta also provides is a rough estimation of what the collective options market thinks is the likelihood that the underlying security will close at a certain price at a certain date.

The formula to arrive at the delta for American options, which differ from European options, is complicated and had me saying ‘oh, the heck with that’ until I found this handy options calculator:

It’s worth reading the ‘calculator’s help’ page (see link on calculator page) to help understand the inputs.”

[What Follows is a Paraphrase Using a Different Ticker Symbol

If I understand this correctly, if we take a ticker symbol such as AAPL (Apple), using the above options calculator, if one enters in AAPL at a strike of 140 for October 15, 2021, and hits ‘calculate’, one sees the delta for a call option is calculated at .2969. Which I believe means the collective options market thinks there roughly a 29.69% chance–let’s call it 30!–that AAPL will close at or above a strike price of 140 by 15 October.]

-Private internet forum