Interest Rates

# Interest Rates

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## Interest Rates

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1. Interest Rates (Chapter 15 BH)

2. Why Don’t They Buy… • Energy efficient appliances, insulation, windows and so on when they redo their homes? • additional cost \$4K upfront • utility bill decrease \$744 • CO2e saved about 11,800 per year.

3. Interest Rate • principle • interest payment • interest rate = payment/principle • (these days often daily, but expressed as a yearly equivalent) • Future Value: The future value of 100 at r% for t years is the amnt of money you will have in t years if invested at r%: principle*(1+r)^t

4. Present Value (PV). Value today of payments in the future. • PV = (1+r) -t * FV • PV of annual payment of AV starting in one year is AV/r.

5. Back to energy saving • If interest is 5% and savings last forever • PV of savings is 14,880 • Cost is 4047 • Present Net Value is 10,833. • On the other hand if the savings only last 5 years the PV of savings is 3221 (look at book for calc) and PNV = -826. • Could also try 10% interest rate.

6. Invest and interest • Obviously high interest and quick depreciation militate against investments. • Even socially nice ones.

8. Market interest rates • Nominal vs. Real • inflation • CPI • If you use real interest rates make sure you are using real prices for the benefits • e.g. nominal electric prices rose by 5%/year, but so did the price of other goods (CPI). • Use nominal prices and nominal interest rate • Use real prices (price/CPI) and real interest = r minus the inflation rate. • Get same answer either way.

9. Borrowing and Saving • Financial system gets paid to round up your savings and lend them to someone. • Difference in rates compensates them for their work and also the risk of the loan, which they bare and you do not.

10. Risk • Treasury bonds are really as guaranteed as you can get. You will get your \$ back. Hence no risk. • Corporate bonds—more risk so you get a higher rate of return to pay you for taking the risk. • Stocks—S&P 500 is a good index (Russel 2000 is a little better). Higher rate of return yet, but you can gain or lose 4% of your money in one day!

11. Risk Reality • 1. If you look only at the post war period then stocks look great relative to bonds. But if you include pre-war bonds and stocks look more similar in their returns. • 2. Your greatest risk is your human capital risk. Disability is not so uncommon and has a far greater effect on your lifetime income than the stock market.

12. Price of Risk • (Advanced Topic) • Investor can hold the S&P itself. Eliminates idiosyncratic risk. Intel goes up and AMD down. Together less risk than alone. • Stocks are priced based on their tendency to rise and fall with the market (S&P). • Ones that go up and down in market cycle faster than the market have the most risk.

13. Public Projects • I want to build a dam. Benefits from electricity, irrigation and flood control all come in the future. Costs all come now. • High interest rate = little PV benefits • Low interest rate = big PV benefits • Which interest rate is “right?”

14. Social Discount Rate • Pure: I believe that all people are too present oriented and want my government to compensate for that. That is, I wouldn’t invest in the dam, but I think they should. • Confused: Global warming is an externality. I want it stopped. I want government to stop it. Here I don’t see why they should use a lower interest rate—they should just price the externality.

15. Risk in Public Projects • There is a way of stopping global climate change. (a hypothetical) • It’s expected costs are a little larger than its expected benefits at the market rate of interest (around 10%, the return, nominal, on the s&p 500) • Would you do it anyway? • Do you insure your house against fire? • Would you buy planet fire insurance?

16. Vexed Question • I hold with the conservatives: • for the same type of project, the gov’t and the private sector should be using the same rates

17. Socially Responsible Investing • A bet against dirty companies. • Tobacco; nuclear; alcohol; defense; • Good record of compliance • Loses diversification • Costs money to do the “screens” • Gives investors a “warm glow”; might work for workers too—but nuclear employees might think that nuclear is cool.

18. Benefit Cost Analysis • “if the benefits to whomsoever they may accrue are in excess of the estimated costs.” • Criteria for public projects

19. Tellico Dam • Outline of story: (Chapt 17) • Dam was mostly built • Snail darter discovered • ESA invoked • G_d squad—interagency group to determine whether to allow extinction. • Found defect in BCA • Dam built and darter survived • Development benefits never happened.

20. Ratio? Max PNV not ratio. When limited funds, then pick projects with highest ratio. With 100million is 10 small better than 5 large? (Not far fetched– a bond to fund water saving projects in CA—projects ranked by BCR)

21. Benefits • Area under demand • could be market good, like corn • could be non-market good like whales

22. costs • usually engineering estimates for structures • got to get all costs • drowned land • drowned Indian villages and historic sites • endangered species • and so on.

23. Alternatives • Big or little dam? • Max concrete s.t. BCA > 0 • Max BCA • When? • Now • Later • Is there an uncertainty that will be resolved if you wait? Is the project marginal with 10 years ago energy prices? Would it be a go now?

24. To BCA or Not to BCA • It is a screen to get rid of truly awful projects. • Like an EIS/EIR it can be manipulated. • If permitted it could be litigated. • Requiring a BCA for environmental regulations is controversial. In practice we do that here in CA and still have the toughest environmental laws. • Perhaps it is an important part of being able to have tough environmental laws—efficient ones are cheaper.