Does the P/E ratio not apply to bond ETFs?
The simple answer is technically bonds don't have earnings, hence no P/E. What I think the OP is really asking how do I compare stock and bond ETFs. Some mature stocks exhibit very similar characteristics to bonds, so at the margin if you are considering investing between 2 such investments that provide stable income in the form of dividends, you might want to use the dividend/price ratio (D/P) of the stock and compare it to the dividend yield of the bond. If you go down to the basics, both the bond and the stock can be considered  the present value of all future expected cashflows. The cash that accrues to the owner of the stock is future dividends and for the bond is the coupon payments. If a company were to pay out 100% of its earnings, then the dividend yield D/P would be conveniently E/P. For a company with P/E of 20 that paid out it's entire earnings, one would expect D/P = 1/20 = 5% This serves as a decent yard stick in the short term ~ 1 year to compare mature stock etfs with stable prospects vs bond funds since the former will have very little expected price growth (think utilities), hence they both compete on the cashflows they throw off to the investor. This comparison stops being useful for stock ETFs with higher growth prospects since expected future cashflows are much more volatile. This comparison is also not valid in the long term since bond ETFs are highly sensitive to the yield curve (interest rate risk) and they can move substantially from where they are now. A bond fund has a 5% yield. You can take 1/.05 and think of it as a 20 P/E.  I wouldn't, because no one else does, really. An individual bond has a coupon yield, and a YTM, yield to maturity. A bond fund or ETF usually won't have a maturity, only a yield. How would you compute the earnings for governments that are some of the main issuers of bonds and debt? When governments run deficits they would have a negative earnings ratio that makes the calculation quite hard to evaluate.
"There are a few reasons why an index mutual fund may be preferable to an ETF: I looked at the iShare S&P 500 ETF and it has an expense ratio of 0.07%.  The Vanguard Admiral S&P 500 index has an expense ratio of 0.05% and the Investor Shares have an expense ratio of 0.17%, do I don't necessarily agree with your statement ""admiral class Vanguard shares don't beat the iShares ETF""." "Your question asks us to explain why a false statement is true.  From the point of view of an investor, a high price to earnings ratio is not necessarily desirable. From the point of view of an investor, a desirable stock is one that is likely to provide future dividends or price increases that more than compensates for the risk of the stock.  This information cannot be inferred from the P/E ratio. So what does the P/E ratio tell us? The P/E ratio measures a stock's current price (i.e., the market's belief about its future earnings) divided by its recent past earnings.  A high ratio means the market thinks earnings in the future will be higher than they are now and have therefore bid the price up.  These can thought of as expensive stocks, and are often called ""growth"" stocks because their price is driven by the market's belief in future growth. Some individual high P/E stocks do live up to or exceed the market's expectation, but there's no evidence that this happens enough that they are more desirable as a group than low P/E stocks. If anything, the empirical evidence goes the other way." "Following comments to your question here, you posted a separate question about why SPY, SPX, and the options contract don't move perfectly together.  That's here Why don't SPY, SPX, and the e-mini s&p 500 track perfectly with each other? I provided an answer to that question and will build on it to answer what I think you're asking on this question.  Specifically, I explained what it means that these are ""all based on the S&P.""  Each is a different entity, and different market forces keep them aligned.  I think talking about ""technicals"" on options contracts is going to be too confusing since they are really a very different beast based on forward pricing models, so, for this question, I'll focus on only SPY and SPX. As in my other answer, it's only through specific market forces (the creation / redemption mechanism that I described in my other answer), that they track at all.  There's nothing automatic about this and it has nothing to do with some issuer of SPY actually holding stock in the companies that comprise the SPX index. (That's not to say that the company does or doesn't hold, just that this doesn't drive the prices.)  What ever technical signals you're tracking, will reflect all of the market forces at play.  For SPX (the index), that means some aggregate behavior of the component companies, computed in a ""mathematically pure"" way.  For SPY (the ETF), that means (a) the behavior of SPX and (b) the behavior of the ETF as it trades on the market, and (c) the action of the authorized participants.  These are simply different things. Which one is ""right""?  That depends on what you want to do.  In theory you might be able to do some analysis of technical signals on SPY and SPX and, for example, use that to make money on the way that they fail to track each other.  If you figure out how to do that, though, don't post it here.  Send it to me directly. :)" There's really no right or wrong answer here because you'll be fine either way. If you've investing amounts in the low 5 figures you're likely just getting started, and if your asset allocation is not optimal it's not that big a deal because you have a long time horizon to adjust it, and the expense ratio differences here won't add up to that much. A third option is Vanguard ETFs, which have the expense ratio of Admiral Shares but have lower minimums (i.e. the cost of a single share, typically on the order of $100). However, they are a bit more advanced than mutual funds in that they trade on the market and require you to place orders rather than just specifying the amount you want to buy. A downside here is you might end up with a small amount of cash that you can't invest, since you can initially only buy whole numbers of ETFs shares. So what I'd recommend is buying roughly the correct number of ETFs shares you want except for your largest allocation, then use the rest of your cash on Admiral Shares of that (if possible). For example, let's say you have $15k to invest and you want to be 2/3 U.S. stock, 1/6 international stock, and 1/6 U.S. bond. I would buy as many shares of VXUS (international stock ETF) and BND (U.S. bond ETF) as you can get for $2500 each, then whatever is left over (~$10k) put into VTSAX (U.S. stock Admiral Shares mutual fund). How you use the metric is super important.   Because it subtracts cash, it does not represent 'value'.  It represents the ongoing financing that will be necessary if both the equity plus debt is bought by one person, who then pays himself a dividend with that free cash.   So if you are Private Equity, this measures your net investment at t=0.5, not the price you pay at t=0.  If you are a retail investor, who a) won't be buying the debt, b) won't have any control over things like tax jurisdictions, c) won't be receiving any cash dividend, etc etc .... the metric is pointless. There is no margin call. Inverse ETFs use derivatives that would lose value in the case you describe though this doesn't force a margin call as you may be misunderstanding how these funds are constructed. "Yes, there are non-stock analogs to the Price/Earnings ratio. Rental properties have a Price/Rent ratio, which is analogous to stocks' Price/Revenue ratio.  With rental properties, the ""Cap Rate"" is analogous to the inverse of the Price/Earnings ratio of a company that has no long-term debt. Bonds have an interest rate.  Depending on whether you care about current dividends or potential income, the interest rate is analogous to either a stock's dividend rate or the inverse of the Price/Earnings ratio." The Vanguard Short-Term Bond Index mutual fund (VBIRX) might fit your need. Apart from 2008, it has only had one single quarter of negative returns, and has always had positive annual returns. If you're looking for an ETF, you might consider iShares Barclays 1-3 Year Credit Bond (CSJ).