I am a complete nerd when it comes to finances, and programming. Since I couldn't find a simulator to answer the title question, I decided to seek out answering it myself using Shiller's data. The idea is one that is obvious at face value but one that I think a lot of people can't quite wrap their minds around... that is, the market ebb and flow directly impacts our FIRE plans much more than we think. To use an analogy, if you're putting a boat into the ocean... running out when the water is receding can get you there much faster/smoother than deciding to run into the water as it's peaking on the shore and dealing with a shallow launch. The ocean is easy to anticipate in these situations, however the markets we watch... not so much. Getting out of the market when we're in a recession is ideal... though usually the opposite happens and we bail after a bull, just in time for the market to recede.

I wrote this a couple years ago and will update the numbers to include that last two years if people are interested... I can also make the salaries and savings rates a bit more aggressive (30%, 40%, 50%) to match what many in the FIRE community are working towards. Let me know your thoughts. It's all just variables in the program, easy to adjust :)

I came up with this first pass simplistic model, to outline what a difference a decade can make in when you started your working career. I'm fascinated by this, although it doesn't come as any surprise that getting horrible returns (or a recession) just before retirement would be a bad thing, it is still interesting to think that our ability (or rather the ease at which we get there) to create financial freedom from the market also depends on factors outside of our control.

Modeling Wealth Accumulation:

In this example I decided to explore what happens when a person consistently saves over their career. For this one I decided to make this accumulation phase 40 years (which could roughly correlate to someone starting to work at 22 and retiring at 62). I could tweak these numbers (and will in future models) but decided to just keep it simple for this first pass. So in this example we will assume the following:

• Starting Salary (in 2016 dollars) $30,000; individual saves 15% of salary every year for 40 years

• Annual salary raises of inflation 1.25% (which would bring the persons salary to $48,699 at the age of 62, in 2016 dollars)

• (CPI) numbers are used in order to factor out inflation - or bring all examples to 2016 dollars. This allows us to compare market conditions in 1880s (using 2016 dollars) based on the above assumptions, to get apples to apples comparison of performance. Basically, we're not looking at the actual growth of your money in real value, but rather the growth minus inflation... or what your buying power would increase to. (It does no good to say today... yay I'll have $1,000,000 in retirement in 2050... if things cost twice as much in 2050 as they do today, then it's be better to think of that as you'll actually only have $500,000 in 2016 dollars once you reached 2050.

Results:

Over a career of 40 years with an initial salary of $30,000 (2016 dollars) and a 1.25% raise each year, setting aside 15% of your salary towards retirement... you would have set aside a total of $231,703 (2016 dollars) into your retirement account. The worst year to have started working would have been 1881, because a combination of inflation an lackluster market conditions in 1915-1920 would conspire to inhibit your retirement account as it reached the finish line. Despite 40 years of compounding and growth, you'd end up with just $370,769 in 2016 dollars (knowing what we know about the great depression... you'd likely experience a roller coaster in retirement as you'd see your account skyrocket in the 20's only to CRASH hard in 1929). It's no wonder my great grandfathers generation was so conservative when it came to investing. Their parents lived this, and they grew up in that environment.

The best year to have started your career would have been 1926, makes sense that starting your accumulation phase just as the depression hit would award you a starting point of buying equities on extreme sale. This is why people shouldn't run from recession markets but rather embrace them for the discount that they are. Strong market conditions in the late 60's led this person to a final figure of $2,110,297

Another interesting point is just how big a difference a few years can make... based on when you started accumulating. Someone who started working in 1968 would have seen their retirement account grow to $1,228,427 by 1998... but someone starting just two years later would have ended up with $692,122 because the last year before retirement they would have been hit by the dot com bust.

That's an anomaly, the median result of that kind of accumulation period is to end up somewhere in the $900K-$1.1M range. About half of all results fell in that range. But there were periods of time where the market continuously was above it... example starting your career between 1912 and 1934 always left you with above $1.1 million... and a median return around $1.7 million, with four of the cycles ending with above $2 million.

This brings me to an important point about this model... it's not all that ideal because people tend to move towards more conservative investments (introducing bonds) as they get closer to retirement. I'm going to track down the inflation adjusted bond return numbers and create an Asset Allocation situation for my next model that will follow this framework but have someone shift slowly towards more conservative investments in the later years of their accumulation phase. Also, what ends up happening is that people who don't quite have enough just work a few years longer... so the strict 40 years isn't all that realistic... but still helps to hammer down the point that even if you're diligent with savings, the market factors still dictate a bit of when you can actually pull the plug on working.

What might be more meaningful is to look at how many years (from each start date) it takes to accumulate say $1.5M by saving 15% of your salary every year (using the above figures 15% savings of a $30K salary that grew to $48,699 over your career -- all figures adjusted for inflation to be in today's dollars).

Here are the results...
YEAR STARTED: 1871 bank passes $1.5M after 53 years
YEAR STARTED: 1872 bank passes $1.5M after 52 years
YEAR STARTED: 1873 bank passes $1.5M after 51 years
YEAR STARTED: 1874 bank passes $1.5M after 51 years
YEAR STARTED: 1875 bank passes $1.5M after 50 years
YEAR STARTED: 1876 bank passes $1.5M after 49 years
YEAR STARTED: 1877 bank passes $1.5M after 49 years
YEAR STARTED: 1878 bank passes $1.5M after 49 years
YEAR STARTED: 1879 bank passes $1.5M after 48 years
YEAR STARTED: 1880 bank passes $1.5M after 47 years
YEAR STARTED: 1881 bank passes $1.5M after 46 years
YEAR STARTED: 1882 bank passes $1.5M after 45 years
YEAR STARTED: 1883 bank passes $1.5M after 45 years
YEAR STARTED: 1884 bank passes $1.5M after 44 years
YEAR STARTED: 1885 bank passes $1.5M after 43 years
YEAR STARTED: 1886 bank passes $1.5M after 42 years
YEAR STARTED: 1887 bank passes $1.5M after 41 years
YEAR STARTED: 1888 bank passes $1.5M after 40 years
YEAR STARTED: 1889 bank passes $1.5M after 46 years
YEAR STARTED: 1890 bank passes $1.5M after 46 years
YEAR STARTED: 1891 bank passes $1.5M after 45 years
YEAR STARTED: 1892 bank passes $1.5M after 44 years
YEAR STARTED: 1893 bank passes $1.5M after 43 years
YEAR STARTED: 1894 bank passes $1.5M after 50 years
YEAR STARTED: 1895 bank passes $1.5M after 50 years
YEAR STARTED: 1896 bank passes $1.5M after 49 years
YEAR STARTED: 1897 bank passes $1.5M after 48 years
YEAR STARTED: 1898 bank passes $1.5M after 47 years
YEAR STARTED: 1899 bank passes $1.5M after 46 years
YEAR STARTED: 1900 bank passes $1.5M after 50 years
YEAR STARTED: 1901 bank passes $1.5M after 49 years
YEAR STARTED: 1902 bank passes $1.5M after 48 years
YEAR STARTED: 1903 bank passes $1.5M after 48 years
YEAR STARTED: 1904 bank passes $1.5M after 47 years
YEAR STARTED: 1905 bank passes $1.5M after 46 years
YEAR STARTED: 1906 bank passes $1.5M after 46 years
YEAR STARTED: 1907 bank passes $1.5M after 45 years
YEAR STARTED: 1908 bank passes $1.5M after 44 years
YEAR STARTED: 1909 bank passes $1.5M after 45 years
YEAR STARTED: 1910 bank passes $1.5M after 44 years
YEAR STARTED: 1911 bank passes $1.5M after 43 years
YEAR STARTED: 1912 bank passes $1.5M after 42 years
YEAR STARTED: 1913 bank passes $1.5M after 41 years
YEAR STARTED: 1914 bank passes $1.5M after 40 years
YEAR STARTED: 1915 bank passes $1.5M after 39 years
YEAR STARTED: 1916 bank passes $1.5M after 38 years
YEAR STARTED: 1917 bank passes $1.5M after 38 years
YEAR STARTED: 1918 bank passes $1.5M after 37 years
YEAR STARTED: 1919 bank passes $1.5M after 36 years
YEAR STARTED: 1920 bank passes $1.5M after 36 years
YEAR STARTED: 1921 bank passes $1.5M after 37 years
YEAR STARTED: 1922 bank passes $1.5M after 36 years
YEAR STARTED: 1923 bank passes $1.5M after 37 years
YEAR STARTED: 1924 bank passes $1.5M after 37 years
YEAR STARTED: 1925 bank passes $1.5M after 36 years
YEAR STARTED: 1926 bank passes $1.5M after 37 years
YEAR STARTED: 1927 bank passes $1.5M after 36 years
YEAR STARTED: 1928 bank passes $1.5M after 36 years
YEAR STARTED: 1929 bank passes $1.5M after 35 years
YEAR STARTED: 1930 bank passes $1.5M after 34 years
YEAR STARTED: 1931 bank passes $1.5M after 34 years
YEAR STARTED: 1932 bank passes $1.5M after 36 years
YEAR STARTED: 1933 bank passes $1.5M after 39 years
YEAR STARTED: 1934 bank passes $1.5M after 49 years
YEAR STARTED: 1935 bank passes $1.5M after 49 years
YEAR STARTED: 1936 bank passes $1.5M after 49 years
YEAR STARTED: 1937 bank passes $1.5M after 48 years
YEAR STARTED: 1938 bank passes $1.5M after 47 years
YEAR STARTED: 1939 bank passes $1.5M after 47 years
YEAR STARTED: 1940 bank passes $1.5M after 46 years
YEAR STARTED: 1941 bank passes $1.5M after 45 years
YEAR STARTED: 1942 bank passes $1.5M after 44 years
YEAR STARTED: 1943 bank passes $1.5M after 46 years
YEAR STARTED: 1944 bank passes $1.5M after 45 years
YEAR STARTED: 1945 bank passes $1.5M after 46 years
YEAR STARTED: 1946 bank passes $1.5M after 45 years
YEAR STARTED: 1947 bank passes $1.5M after 45 years
YEAR STARTED: 1948 bank passes $1.5M after 45 years
YEAR STARTED: 1949 bank passes $1.5M after 46 years
YEAR STARTED: 1950 bank passes $1.5M after 45 years
YEAR STARTED: 1951 bank passes $1.5M after 45 years
YEAR STARTED: 1952 bank passes $1.5M after 44 years
YEAR STARTED: 1953 bank passes $1.5M after 43 years
YEAR STARTED: 1954 bank passes $1.5M after 43 years
YEAR STARTED: 1955 bank passes $1.5M after 42 years
YEAR STARTED: 1956 bank passes $1.5M after 41 years
YEAR STARTED: 1957 bank passes $1.5M after 41 years
YEAR STARTED: 1958 bank passes $1.5M after 40 years
YEAR STARTED: 1959 bank passes $1.5M after 39 years
YEAR STARTED: 1960 bank passes $1.5M after 38 years
YEAR STARTED: 1961 bank passes $1.5M after 38 years
YEAR STARTED: 1962 bank passes $1.5M after 37 years
YEAR STARTED: 1963 bank passes $1.5M after 36 years
YEAR STARTED: 1964 bank passes $1.5M after 48 years
YEAR STARTED: 1965 bank passes $1.5M after 48 years
YEAR STARTED: 1966 bank passes $1.5M after 47 years
YEAR STARTED: 1967 bank passes $1.5M after 46 years
YEAR STARTED: 1968 bank passes $1.5M after 45 years
YEAR STARTED: 1969 bank passes $1.5M after 44 years
YEAR STARTED: 1970 bank passes $1.5M after 44 years
YEAR STARTED: 1971 bank passes $1.5M after 43 years

What I found particularly remarkable about these results is that someone who started working in 1931 setting aside 15% of their modest pay reached $1.5M in just 34 years... while someone who started just 3 years later in 1934 had to work an extra 15 years longer to achieve the same level of financial security. A combination of inflation in the 70's and a 50% surge in the market in 1933 that got the compounding started early, created this disparity.*

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As I mentioned above, I'm open to suggestions on how to change the variables to get a more meaningful study of the market as it would fit the FIRE community. My guess is that a larger savings rate and shorter period of accumulation smooths these figures off a bit, however the actual year you start to save will still have a significant say in how market compounding impacts your FIRE timeline.