How much is an asset producing $X/month is worth?
The simplest way is just to compute how much money you'd have to have invested elsewhere to provide a comparable return. For example, if you assume a safe interest rate of 2.3% per year, you would need to have about $520,000 to get $1,000/month.
&gt;Money is accumulated work, not debt.  I think you're slightly missing the point, but I do think the post does deal with that indirectly. Loddars are a store of value (they store current and future value of work). By promising to pay X loddars I've promised to do X amount of work. Similarly, the number of loddars I have is proportional to the amount of work I have done, or am expected to be able to do.  Which is why  &gt;The economy functions on work, not promises. The farmer may promise a million bushels of apples and the hunter may promise a million deer, but that's just fantasy.  Slightly misses the point. The farmer, the hunter, and the cooper can promise the sky and that's fantasy. But that's not really a criticism because it's not a realistic possibility.   The farmer, hunter, and cooper can also promise feasible things, like 10 sacks of potatoes, 5 deer skins, and 12 barrels to be delivered ten days from today. Because these promises are feasible (barring someone doesn't die) and because they've reliably delivered in the past, we can assume that their promises are good. Their promises are valuable because they are reliable producers.  And if a meteorite falls out of the sky to strike the hunter dead, we can actually measure the impact of his death and price it. If we know the hunter produces ~100 deer skins per year, and he dies suddenly, we could actually have planned ahead for such an eventuality. On the basis of their past performance, we can reliably price the value of their future promises. And if they don't perform, we can price that too.  How would we do that? Maybe each producer pays, as a premium, a part of their output into a central pot that they/their heirs/society can draw from if one of them dies, or under-produces. We can value this pot in loddars, and maybe this pot can even underwrite a few loans of loddars to others.   That being said I'm not sure I understand your bit about Krugman and how it relates? "Why there is this huge difference? I am not able to reconcile Yahoo's answer of 5.75%, even using their definition for ROA of: Return on Assets Formula: Earnings from Continuing Operations / Average Total Equity This ratio shows percentage of Returns to Total Assets of the company.   This is a useful measure in analyzing how well a company uses its   assets to produce earnings. I suspect the ""Average Total Equity"" in their formula is a typo, but using either measure I cannot come up with 5.75% for any 12-month period. I can, however, match MarketWatch's answer by looking at the 2016 fiscal year totals and using a ""traditional"" formula of Net Income / Average Total Assets: I'm NOT saying that MatketWatch is right and Yahoo is wrong - MW is using fiscal year totals while Yahoo is using trailing 12-month numbers, and Yahoo uses ""Earnings from Continuing Operations"", but even using that number (which Yahoo calculates) I am not able to reconcile the 5.75% they give." Because they receive compensation (generally interest + dividends) for loaning out the shares. I own an asset X.   Somebody else wants to borrow asset X for some time period.   I agree to loan them asset X in return for some form of compensation (generally a rate of interest plus, in this specific case, any dividend payments).  The reasons why I own asset X, and why they want to borrow asset X are irrelevant to the transaction. The only relevant points are the amount of compensation and the risk that they might default on the loan. This applies equally well to shares as to money or any other kind of loan-able asset. What's the present value of using the payment plan? In all common sense the present value of a loan is the value that you can pay in the present to avoid taking a loan, which in this case is the lump sum payment of $2495.  That rather supposes the question is a trick, providing irrelevant information about the stock market. However, if some strange interpretation is required which ignores the lump sum and wants to know how much you need in the present to pay the loan while being able to make 8% on the stock market that can be done. I will initially assume that since the lender's APR works out about 9.6% per month that the 8% from the stock market is also per month, but will also calculate for 8% annual effective and an 8% annual nominal rate. The calculation If you have $x in hand (present value) and it is exactly enough to take the loan while investing in the stock market, the value in successive months is $x plus the market return less the loan payment.  In the third month the loan is paid down so the balance is zero. I.e. So the present value of using the payment plan while investing is $2569.37. You would need $2569.37 to cover the loan while investing, which is more than the $2495 lump sum payment requires.  Therefore, it would be advisable to make the lump sum payment because it is less expensive: If you have $2569.37 in hand it would be best to pay the lump sum and invest the remaining $74.37 in the stock market.  Otherwise you invest $2569.37 (initially), pay the loan and end up with $0 in three months. One might ask, what rate of return would the stock market need to yield to make it worth taking the loan? The APR proposed by the loan can be calculated.   The present value of a loan is equal to the sum of the payments discounted to present value.  I.e. with  ∴ by induction  So by comparing the $2495 lump sum payment with $997 over 3 x monthly instalments the interest rate implied by the loan can be found. Solving for r If you could obtain 9.64431% per month on the stock market the $x cash in hand required would be calculated by This is equal to the lump sum payment, so the calculated interest is comparable to the stock market rate of return.  If you could gain more than 9.64431% per month on the stock market it would be better to invest and take the loan. Recurrence Form Solving the recurrence form shows the calculation is equivalent to the loan formula, e.g. becomes v[m + 1] = (1 + y) v[m] - p where v[0] = pv where In the final month v[final] = 0, i.e. when m = 3 Compare with the earlier loan formula: s = (d - d (1 + r)^-n) / r They are exactly equivalent, which is quite interesting, (because it wasn't immediately obvious to me that what the lender charges is the mirror opposite of what you gain by investing). The present value can be now be calculated using the formula. Still assuming the 8% stock market return is per month. If the stock market yield is 8% per annum effective rate and if it is given as a nominal annual yield, 8% compounded monthly "An answer can be found in my book, ""A Modern Approach to Graham and Dodd Investing,"" p. 89 http://www.amazon.com/Modern-Approach-Graham-Investing-Finance/dp/0471584150/ref=sr_1_1?s=books&ie=UTF8&qid=1321628992&sr=1-1 ""If a company has no sustained cash flow over time, it has no value...If a company has positive cash flow but economic earnings are zero or less, it has a value less than book value and is a wasting asset. There is enough cash to pay interim dividends, bu the net present value of the dividend stream is less than book value."" A company with a stock trading below book value is believed to be ""impaired,"" perhaps because assets are overstated. Depending on the situation, it may or may not be a bankruptcy candidate." 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. Dummy example to explain this. Suppose your portfolio contained just two securities; a thirty year US government bond and a Tesla stock. Both of those position are currently valued at $1mm. The Tesla position however is very volatile with its daily volatility being about 5% (based on the standard deviation of its daily return) whole there bond's daily volatility is 1%. Then the Tesla position is 5/6 of your risk while being only 1/2 of the portfolio.   Now if in month the Tesla stock tanks to half is values then. Then it's risk is half as much as before and so it's total contribution to risk has gone down. Since I'm missing the shortest and simplest answer, I'll add it: A car also doesn't offer dividends, yet it's still worth money. A $100 bill doesn't offer dividends, yet people are willing to offer services, or goods, or other currencies, to own that $100 bill. It's the same with a stock. If other people are willing to buy it off you for a price X, it's worth at least close to price X to you. In theory the price X depends on the value of the assets of the company, including unknown values like expected future profits or losses. Speaking from experience as a trader, in practice it's very often really just price X because others pay price X.