第十一章：收益和风险：资本资产定价模型1.系统性风险通常是不可分散的，而非系统性风险是可分散的。
但是，系统风险是可以控制的，这需要很大的降低投资者的期望收益。
2.（1）系统性风险（2）非系统性风险（3）都有，但大多数是系统性风险（4）非系统性风险（5）非系统性风险（6）系统性风险3.否，应在两者之间4.错误，单个资产的方差是对总风险的衡量。
5.是的，组合标准差会比组合中各种资产的标准差小，但是投资组合的贝塔系数不会小于最小的贝塔值。
6. 可能为0，因为当贝塔值为0 时，贝塔值为0 的风险资产收益=无风险资产的收益，也可能存在负的贝塔值，此时风险资产收益小于无风险资产收益。
7.因为协方差可以衡量一种证券与组合中其他证券方差之间的关系。
8. 如果我们假设，在过去3 年市场并没有停留不变，那么南方公司的股价价格缺乏变化表明该股票要么有一个标准差或贝塔值非常接近零。
德州仪器的股票价格变动大并不意味着该公司的贝塔值高，只能说德州仪器总风险很高。
9. 石油股票价格的大幅度波动并不表明这些股票是一个很差的投资。
如果购买的石油股票是作为一个充分多元化的产品组合的一部分，它仅仅对整个投资组合做出了贡献。
这种贡献是系统风险或β来衡量的。
所以，是不恰当的。
10. The statement is false. If a security has a negative beta, investors would want to hold the asset to reduce the variability of their portfolios. Those assets will have expected returns that are lower than the risk-free rate. To see this, examine the Capital Asset Pricing Model:E(R S) = R f + S[E(R M) – R f] If S < 0, then the E(R S) < R f11. Total value = 95($53) + 120($29) = $8,515The portfolio weight for each stock is:WeightA = 95($53)/$8,515 = .5913 WeightB = 120($29)/$8,515 = .4087 12.Total value = $1,900 + 2,300 = $4,200So, the expected return of this portfolio is:E(R p) = ($1,900/$4,200)(0.10) + ($2,300/$4,200)(0.15) = .1274 or 12.74%13. E(R p) = .40(.11) + .35(.17) + .25(.14) = .1385 or 13.85%14. Here we are given the expected return of the portfolio and the expected return of each asset in the portfolio and are asked to find the weight of each asset. We can use the equation for the expected return of a portfolio to solve this problem. Since the total weight of a portfolio must equal 1 (100%), the weight of Stock Y must be one minus the weight of Stock X. Mathematically speaking, this means:E(R p) = .129 = .16w X + .10(1 –w X)We can now solve this equation for the weight of Stock X as:.129 = .16w X + .10 – .10w X w X = 0.4833So, the dollar amount invested in Stock X is the weight of Stock X times the total portfolio value, or: Investment in X = 0.4833($10,000) = $4,833.33And the dollar amount invested in Stock Y is:Investment in Y = (1 – 0.4833)($10,000) = $5,166.6715. E(R) = .2(–.09) + .5(.11) + .3(.23) = .1060 or 10.60%16. E(RA) = .15(.06) + .65(.07) + .20(.11) = .0765 or 7.65%E(RB) = .15(–.2) + .65(.13) + .20(.33) = .1205 or 12.05%17. E(R A) = .10(–.045) + .25 (.044) + .45(.12) + .20(.207) = .1019 or 10.19%方差=.10(–.045 – .1019)⌒2 + .25(.044 – .1019)⌒2 + .45(.12 – .1019)⌒2 + .20(.207 – .1019)⌒2 = .00535标准差= (.00535)1/2 = .0732 or 7.32%18. E(R p) = .15(.08) + .65(.15) + .20(.24) = .1575 or 15.75%If we own this portfolio, we would expect to get a return of 15.75 percent.19. a.Boom: E(R p) = (.07 + .15 + .33)/3 = .1833 or 18.33%Bust: E(R p) = (.13 + .03 .06)/3 = .0333 or 3.33%E(Rp) = .80(.1833) + .20(.0333) = .1533 or 15.33%b. Boom: E(R p)=.20(.07) +.20(.15) + .60(.33) =.2420 or 24.20%Bust: E(R p) =.20(.13) +.20(.03) + .60( .06) = –.0040 or –0.40%E(R p) = .80(.2420) + .20( .004) = .1928 or 19.28%P的方差= .80(.2420 – .1928)⌒2 + .20( .0040 – .1928)⌒2 = .0096820.a．Boom: E(R p) = .30(.3) + .40(.45) + .30(.33) = .3690 or 36.90%Good: E(R p) = .30(.12) + .40(.10) + .30(.15) = .1210 or 12.10%Poor: E(R p) = .30(.01) + .40(–.15) + .30(–.05) = –.0720 or –7.20%Bust: E(R p) = .30(–.06) + .40(–.30) + .30(–.09) = –.1650 or –16.50%E(R p) = .20(.3690) + .35(.1210) + .30(–.0720) + .15(–.1650) = .0698 or 6.98%b． p⌒2 = .20(.3690 – .0698)⌒2 + .35(.1210 – .0698)⌒2 + .30(–.0720 – .0698)⌒2 + .15(–.1650 – .0698)⌒2 = .03312p的标准差= (.03312)⌒1/2 = .1820 or 18.20%21. β= .25(.75) + .20(1.90) + .15(1.38) + .40(1.16) = 1.2422.βp = 1.0 = 1/3(0) + 1/3(1.85) + 1/3(βX) βX = 1.1523.E(R i) = R f + [E(R M) – R f] ×βiE(R i) = .05 + (.12 – .05)(1.25) = .1375 or 13.75%24. We are given the values for the CAPM except for the of the stock. We need to substitute these values into the CAPM, and solve for the of the stock. One important thing we need to realize is that we are given the market risk premium. The market risk premium is the expected return of the market minus the risk-free rate. We must be careful not to use this value as the expected return of the market. Using the CAPM, we find:E(R i) = .142 = .04 + .07βi 则βi = 1.4625. E(R i) = .105 = .055 + [E(R M) – .055](.73) 则E(R M) = .1235 or 12.35%26. E(R i) = .162 = R f + (.11 – R f)(1.75).162 = R f + .1925 – 1.75R f则R f = .0407 or 4.07%27. a. E(R p) = (.103 + .05)/2 = .0765 or 7.65%b. We need to find the portfolio weights that result in a portfolio with a of 0.50. We know the 贝塔of the risk-free asset is zero. We also know the weight of the risk-free asset is one minus the weight of the stock since the portfolio weights must sum to one, or 100 percent. So:c. We need to find the portfolio weights that result in a portfolio with an expected return of 9 percent. We also know the weight of the risk-free asset is one minus the weight of the stock since the portfolio weights must sum to one, or 100 percent. So:d. Solving for the of the portfolio as we did in part a, we find:18. ßp = w W(1.3) + (1 –w W)(0) = 1.3w WSo, to find the βof the portfolio for any weight of the stock, we simply multiply the weight of the stock times its β.Even though we are solving for the and expected return of a portfolio of one stock and the risk-free asset for different portfolio weights, we are really solving for the SML. Any combination of this stock and the risk-free asset will fall on the SML. For that matter, a portfolio of any stock and the risk-free asset, or any portfolio of stocks, will fall on the SML. We know the slope of the SML line is the market risk premium, so using the CAPM and the information concerning this stock, the market risk premium is:E(R W) = .138 = .05 + MRP(1.30)MRP = .088/1.3 = .0677 or 6.77%So, now we know the CAPM equation for any stock is:E(R p) = .05 + .0677*贝塔p29. E(R Y) = .055 + .068(1.35) = .1468 or 14.68%E(R Z) = .055 + .068(0.85) = .1128 or 11.28%Reward-to-risk ratio Y = (.14 – .055) / 1.35 = .0630Reward-to-risk ratio Z = (.115 – .055) / .85 = .070630. (.14 – R f)/1.35 = (.115 – R f)/0.85We can cross multiply to get: 0.85(.14 – R f) = 1.35(.115 – R f)Solving for the risk-free rate, we find:0.119 – 0.85R f = 0.15525 – 1.35R f R f = .0725 or 7.25%31.32. [E(R A) – R f]/ A = [E(R B) – R f]/ßBRP A/β A = RP B/β B βB/βA = RP B/RP A33. Boom: E(R p) = .4(.20) + .4(.35) + .2(.60) = .3400 or 34.00%Normal: E(R p) = .4(.15) + .4(.12) + .2(.05) = .1180 or 11.80%Bust: E(R p) = .4(.01) + .4(–.25) + .2(–.50) = –.1960 or –19.60%E(R p) = .35(.34) + .40(.118) + .25(–.196) = .1172 or 11.72%σp⌒2= .35(.34 – .1172)2 + .40(.118 – .1172)2 + .25(–.196 – .1172)2 = .04190σp= (.04190)1/2 = .2047 or 20.47%b. RP i = E(R p) – R f = .1172 – .038 = .0792 or 7.92%c．Approximate expected real return = .1172 – .035 = .0822 or 8.22%1 + E(R i) = (1 + h)[1 + e(r i)]1.1172 = (1.0350)[1 + e(r i)]e(r i) = (1.1172/1.035) – 1 = .0794 or 7.94%Approximate expected real risk premium = .0792 – .035 = .0442 or 4.42%Exact expected real risk premium = (1.0792/1.035) – 1 = .0427 or 4.27%34. w A = $180,000 / $1,000,000 = .18 w B = $290,000/$1,000,000 = .29βp = 1.0 = w A(.75) + w B(1.30) + w C(1.45) + w Rf(0) w C = .33655172Invest in Stock C = .33655172($1,000,000) = $336,551.721 = w A + w B + w C + w Rf 1 = .18 + .29 + .33655172 + w Rf w Rf = .19344828Invest in risk-free asset = .19344828($1,000,000) = $193,448.28w X(.172) + w Y(.0875) + (1 –w X –w Y)(.055)35. E(R p) = .1070 =βp = .8 = w X(1.8) + w Y(0.50) + (1 –w X – w Y)(0)w X = –0.11111 w Y = 2.00000 w Rf = –0.88889Investment in stock X = –0.11111($100,000) = –$11,111.1136. E(R A) = .33(.082) + .33(.095) + .33(.063) = .0800 or 8.00%E(R B) = .33(–.065) + .33(.124) + .33(.185) = .0813 or 8.13%股票A：方差=.33(.082 – .0800)⌒2 + .33(.095 – .0800)⌒2 + .33(.063 – .0800)⌒2 = .00017 标准差=(.00017)⌒1/2 = .0131 or 1.31%股票B：方差=.33(–.065 – .0813)⌒2 + .33(.124 – .0813)⌒2 + .33(.185 – .0813)⌒2 = .01133 标准差= (.01133)1/2 = .1064 or 1064%Cov(A,B) = .33(.092 – .0800)(–.065 – .0813) + .33(.095 – .0800)(.124 – .0813) + .33(.063– .0800)(.185 – .0813) = –.000472ρA,B = Cov(A,B) / （标准差A 标准差B）= –.000472 / (.0131)(.1064) = –.337337. E(R A) = .30(–.020) + .50(.138) + .20(.218) = .1066 or 10.66%E(R B) = .30(.034) + .50(.062) + .20(.092) = .0596 or 5.96%A的方差 =.30(–.020 – .1066)⌒2 + .50(.138 – .1066)⌒2 + .20(.218 – .1066)⌒2 = .00778 2 A的标准差= (.00778)⌒1/2 = .0882 or 8.82%B的方差=.30(.034 – .0596)⌒2 + .50(.062 – .0596)⌒2 + .20(.092 – .0596)⌒2 = .00041B的标准差= (.00041)⌒1/2 = .0202 or 2.02%Cov(A,B) = .30(–.020 – .1066)(.034 – .0596) + .50(.138 – .1066)(.062 – .0596)+ .20(.218 – .1066)(.092 – .0596) = .001732ρA,B = Cov(A,B) / A的标准差*B的标准差= .001732 / (.0882)(.0202) = .970138. a. E(R P) = w F E(R F) + w G E(R G)E(R P) = .30(.10) + .70(.17) = .1490 or 14.90%b. The variance of a portfolio of two assets can be expressed as:标准差= (.18675)⌒1/2 = .4322 or 43.22%39. a. The expected return of the portfolio is the sum of the weight of each asset times the expected return of each asset, so:E(R P) = w A E(R A) + w B E(R B) = .45(.13) + .55(.19) = .1630 or 16.30%c. As Stock A and Stock B become less correlated, or more negatively correlated, the standard deviation of the portfolio decreases.40.(iv) The market has a correlation of 1 with itself.(v) The beta of the market is 1.(vi) The risk-free asset has zero standard deviation.(vii) The risk-free asset has zero correlation with the market portfolio.(viii) The beta of the risk-free asset is 0.b. Firm A: E(R A) = R f + βA[E(R M) – R f]E(R A) = 0.05 + 0.85(0.12 – 0.05) = .1095 or 10.95%Firm B: E(R B) = R f +βB[E(R M) – R f]E(R B) = 0.05 + 1.5(0.12 – 0.05) = .1550 or 15.50%Firm C: E(R C) = R f + βC[E(R M) – R f]E(R C) = 0.05 + 1.23(0.12 – 0.05) = .1358 or 13.58%According to the CAPM, the expected return on Firm C‘s stock should be 13.58 percent. However, the expected return on Firm C‘s stock given in the table is 17 percent. Therefor e, Firm C‘s stock is underpriced, and you should buy it.43. First, we need to find the standard deviation of the market and the portfolio, which are:M的标准差= (.0429)⌒1/2 = .2071 or 20.71%Z 的标准差= (.1783)⌒1/2 = .4223 or 42.23%Now we can use the equation for beta to find the beta of the portfolio, which is:βZ = (相关系数Z,M)*(标准差Z) / 标准差M = (.39)(.4223) / .2071 = .80Now, we can use the CAPM to find the expected return of the portfolio, which is:E(R Z) = R f + βZ[E(R M) – R f] = .048 + .80(.114 – .048) = .1005 or 10.05%。
