如题所述
高顿CFA为你解答:
Safety-firstratio(安全第一比率):
thedistancefromthemeanreturntotheshortfalllevelinunitsofstandarddeviation。平均收益与最低可接受的临界收益的距离有多少个标准差。这个比率越大越好,表明单位风险上的收益较高。
注:Safety-firstratio与sharperatio比较相似,中是无风险收益率,而SFRatio中是最低可接受的临界收益。
Shortfallrisk(亏空风险):
theriskthatportfoliovalueorreturnwillfallbelowtheminimumacceptablelevel(RL,shortfalllevel,thresholdlevel)oversometimehorizon.
亏空风险是指在整个投资期限内,组合的收益低于最小可接受的回报范围。
Safety-firstratio与Shortfallrisk的关系:
Minimizingshortfallrisk=Maximizingsafety-firstratio
最小的亏空风险等于最大的安全第一比率
例:Attheendofthecurrentyear,aninvestorwantstomakeadonationof$20,000touniversitybutdoesnotwanttheyear-endmarketvalueofherportfoliotofallbelow$500,000.Iftheshortfalllevelisequaltotherisk-freerateofreturnandreturnsfromallportfoliosconsideredarenormallydistributed,willbeportfoliothatminimizestheprobabilityoffailingtoachievetheinvestor'sobjectivemostlikelyhavethe:
highestsafety-firstratio?highestSharperatio?
A.NoYes
B.NoNo
C.YesYes
答案:选C
解析:Theportfoliowiththehighestsafety-firstratiominimizestheprobabilitythattheportfolioreturnwillbelessthantheshortfalllevel(givennormality).Inthisproblem,theshortfalllevelisequaltotherisk-freerateofreturnandthusthehighestsafety-firstratioportfoliowillbethesameasthehighestSharperatioportfolio.安全第一比率越大,投资落入达不到临界回报水平区间的概率越小,同时,如果临界水平的收益率等于无风险利率时,则夏普比率与安全第一比率计算的结果是一样的。