It was a quick and imperfect model, I admit, and inflation impacts not only your cash savings (negatively), but also your ability to save in certain approved retirement vehicles (positively). The Fed is having a tough time hitting an inflation target of 2% at the moment, but if we back that 2% out of the rate of growth to account for inflation and hold inflation-adjusted returns at 7%, the model changes to the following, with and without employer matching and Roth.
Code:Years FV Per Year Premium 20 $737,918.86 $36,895.94 $18,895.94 10 $248,696.06 $24,869.61 $6,869.61 5 $103,513.30 $20,702.66 $2,702.66 1 $18,000.00 $18,000.00 $0.00 With Roth and Employer Matching Years FV Per Year Premium 20 $1,250,362.52 $62,518.13 $39,018.13 10 $421,401.66 $42,140.17 $18,640.17 5 $175,397.54 $35,079.51 $11,579.51 1 $30,500.00 $30,500.00 $7,000.00
Still not shown above would be how being able to invest would impact your tax liability due to the potential of deferred income. Any taxes that are avoided is money in your pocket and would actually increase your "premium" requirement.
You wouldn't back the 2% inflation out of the yield for comparison's sake though, as what matters for this comparison is not how much you beat inflation by, but how much you beat the hypothetical scenario (no investing) by.
If anything inflation would increase the gap, as equity prices are positively correlated to inflation. When things go up in price, it is nice to own things that are not fixed to the currency, like equities.
I would think there must be a way to get some decent investment portfolio going though, even in a shitty situation like Dunan has going on. Shit, worst case scenario I would form a corporation and use it to do my investments for me, since just because I can't open an account at another financial institution that shouldn't prevent a company I own from doing so(not knowing anything about the legalities of corporation in Japan, but I guess you would incorporate stateside anyway).
Point is, you should find a way to do it within the law and the rules of your employer, but you shouldn't just give up because it will be worth the hassle in the long run.