Mathguy,
"VWEHX is a bond fund that does not touch principal"
You 'touch principle' whenever you sell shares, and withdraw the proceeds. Principle value changes always occur, as fund NAVs rise and fall. Whenever the fund yields 7.34%, that represents a certain number of dollars. If you withdraw 7% (a certain smaller number of dollars), you reinvest 0.34%, a considerably smaller number of dollars. You don't withdraw principle, you actually add ot it, by buying more shares. Sell shares, you touch principle, buy shares, you add to it.
"that a balanced fund (just because it holds stocks) is riskier (defined as standard deviation of total returns?) than a fund that holds all bonds (regardless of quality?)."
SD of share price changes is higher than SD of yield changes, simply because share prices are more uncertain. SD data for VWEHX over it's lifetime is TR - 8.54%, Y - 2.63%, G - 7.99%, BTW. That is, almost ALL of the SD for VWEHX TR comes from the volatility of the fund NAV, and NOT the volatility of it's yield. And VWEHX is a bond fund, not stock fund.
Now, you might argue that, because of correlation coefficients, the TR of a balanced fund might be lower in risk than either an all stock or all bond fund. But, since we don't know the asset classes that will be in the new fund, nor their percentages, we really can't make this determination. Absent ANY knowledge of the new fund, and infinite knowledge of VWEHX, I consider the new fund much riskier.
"The 1978-1994 data for the bond funds is actually fiscal year Feb-Jan from Vanguard's annual reports."
I have the same data, through 2000. I also have the actual monthly information, which is much more useful to show monthly withdrawals from the fund. As I say, I stopped at 2000, and used the results to develop my investment and withdrawal strategy.
"It looks like both LT Inv Grade and Wellesley have produced higher returns with less risk."
Looks like returns were higher. What about SDs? Finally, will the new fund behave like either? And how do you quantify THAT risk of uncertainty?
"No, I don't know of any specific default hits suffered by VWEHX."
The answer is 2, and I don't know whether it was a complete loss of principle or not. I forget when they occurred, but there was no discernable drop in fund NAV at those times, which were a few years apart.
"The VWEHX NAV bounces around . . . . ."
It's SD was a bit under 8% over it's lifetime. The SD of a typical stock fund is at least double that. Average annualized TR for VWEHX over it's lifetime is 9.77%, average yield was 11%, average capital loss (drop in fund NAV) was -1.23%. None of this behavior can be explained by historic default rates, credit quality, whatever, as your paragraph implies. The fund behavior was what it was. Nothing more, nothing less. And you can expect it to behave in a similar manner, going forward. What do you expect the behavior of the new fund is going to be, going forward?
"Isn't this a "withdraw all the yield" strategy?"
No. Withdrawing 7.34% is the withdraw all the yield strategy. If you withdraw 7%, you reinvest 0.34%, buying more shares. If you withdraw 8%, you are withdrawing more than the yield, touching principle. Withdrawing 70% of the yield strategy would withdraw 5.14%, reinvesting 2.2% of the yield.
I would now argue that using VWEHX, instead of the new 5% fund is considerably less risky, for all of the same arguments in this post!
"it's not even sustainable (due to the NAV erosion). "
Actually, withdrawing any part of, including ALL of the yield, is sustainable. That is, the income will last forever. What doesn't sustain is whether or not that income adjusts for inflation, nor the value you have in the fund. With a bond fund, the ONLY way to have the yield adjust for inflation is if the fund itself is a fund of TIPS, or if you withdraw only a portion of the yield and reinvest the rest of the yield.
You CAN have a stock fund the produces income (dividend yields) that grow with inflation. The dividends themselves have to grow by that amount. In addition, if you withdraw a portion of the dividend yield, you have a second mechanism that might grow the real withdraw amount.
In summary, I was asked why I considered an investment, today, in VWEHX to be considerably less risky than an investment in a new, untested fund. I've given the reasons. Then the conversatiion turned to discussing those risks in terms of a 7% rate of withdrawal. It's still considerably less risky, based either on past performance (of which the new fund has none!) or expectations. Withdrawing 7% from VWEHX over it's lifetime would not have been disasterous. Withdrawing 7% from a fund that yields 7.34% won't be disasterous, going forward.
It's as simple as that.
I'm discussing this with you, since you understand the numbers. helmut doesn't. For example, rather than looking at the complete history for VWEHX, as you have done, he chooses the last 10 years, and tries to make some point. But why 10? Why not 5? Turns out that the all time LOW for VWEHX was almost exactly 5 years ago, and it's been uphill ever since! How would that affect things (higher, rather than lower, fund NAV).
Just something thrown out, by the relief pitcher!