I saw this thread a while back, but only now decided to throw my 2 cents in and hopefully will not cause more confusion. I cannot read the OP's mind, but I suppose the question could be rephrased as follows: "Was your own retirement financial situation within the range of past outcomes shown by FIRECalc?".
One can set up a simple run to see the outcome range for himself. Use a $1M portfolio, an annual expense of $40K (for 4%WR), an AA of middling 50 Long Interest / 50 Total Market, no other income. I use a 10 year run because most ER's here who use FIRECalc have been retired for a shorter time than that.
And FIRECalc says that at the end of 10 years, using history as a guide, your $1M could have shrunk to $386K or grown to $2.178M. That's a huge range of 5.6:1.
I think it is rare that an individual result would fall outside the above range. I think all posters here are within this range. Well, I am sure there are some who dropped out of the forum and went back to work with their stash decimated, and the respondents here are a self-selecting group. But I hasten to add that the failed ER's most likely caused the failure themselves by buying high/selling low, or by overspending.
But that last observation brings us back to the original premise: FIRECalc shows what could have happened if you invested and spent exactly as your input data to the program. And I do not see myself doing that. I could be higher or lower, depending on how I invest and how I spend. Still, that's a huge range and one has to do a lot of lucky or bad things to fall outside.
Allow me to digress a bit here. I wonder if people who rebalance exactly on Jan 1st and control their spending to an exact WR do that to improve the chance that their outcome will stay within the realm of FIRECalc result. Even so, it's still a hell of a range though.
Finally, I remember another ER forum where a 50/50 hypothetical portfolio was tracked through the lost decade of 2000-2010. I have not been back to that forum, but as I recall the result was miserable, and did not look to be much higher than the $386K worst case shown by FIRECalc. And of course, FIRECalc by now has already incorporated that 10-year period.
So, to really answer the question of whether a user of FIRECalc (with all the caveats of his investment and spending habits being exactly like his data input) in 2000 would find his result within the program output range (as history unfolds as the result of 2000-2010 was not known back in 2000), I would have to see where the 2000-2010 period fits within all the previous 10-year periods. Ah, that takes a bit of work and I do not feel like doing it now, but suspect that the 2000-2010 did not set a new worst case.
PS. FIRECalc's results are inflation-adjusted. So, in the worst case of $386K after 10 years, our hapless retiree has more than $386K in nominal dollars. That may help alleviate his pain, as he now has more money (worth less) to count.
PPS. OK, I got the answer about the 2000-2010 period. It was lousy, but still far above the worst case 10-year periods of 1912-1922 and 1973-1983.