Every named formula in the series, chapter by chapter, each with its meaning in words and a link to the worked example.

105Formulas
21Chapters

Chapter 2 · Risk and return, the types

r¯=1n∑t=1nrt\bar{r} = \frac{1}{n} \sum_{t=1}^{n} r_t

In words, the arithmetic mean adds the yearly returns and divides by how many there are.

Arithmetic and geometric means

G=(∏t=1n(1+rt))1/n−1G = \left( \prod_{t=1}^{n} (1 + r_t) \right)^{1/n} - 1

In words, the geometric mean multiplies the yearly growth factors, takes the n-th root and subtracts one.

Arithmetic and geometric means

rextannual=(1+R)1/T−1r_{ ext{annual}} = (1 + R)^{1/T} - 1

In words, the annualised return is one plus the total return raised to one over the number of years, minus one.

Annualising

σ=1n−1∑t=1n(rt−r¯)2\sigma = \sqrt{ \frac{1}{n-1} \sum_{t=1}^{n} (r_t - \bar{r})^2 }

In words, the standard deviation squares each year's distance from the mean, averages those squares and takes the square root.

Standard deviation

S=r¯−rfσS = \frac{\bar{r} - r_f}{\sigma}

In words, the Sharpe ratio is the average return above the risk-free rate divided by the standard deviation.

Sharpe and Sortino ratios

βi=Cov⁡(ri,rm)σm2=ρimσiσm\beta_i = \frac{\operatorname{Cov}(r_i, r_m)}{\sigma_m^2} = \rho_{im} \, \frac{\sigma_i}{\sigma_m}

In words, beta is the covariance of the stock with the market divided by the market's variance, which equals the correlation times the stock's standard deviation over the market's.

Beta, alpha and the information ratio

Chapter 3 · Probability and statistics for investors

E[X]=∑ipixi\mathbb{E}[X] = \sum_{i} p_i \, x_i

In words, the expected value is the sum of each outcome multiplied by its probability.

Expected value and variance

σ2=∑ipi(xi−E[X])2\sigma^2 = \sum_{i} p_i \, (x_i - \mathbb{E}[X])^2

In words, the variance is the probability-weighted average of each outcome's squared distance from the expected value.

Expected value and variance

G≈μ−σ22G \approx \mu - \frac{\sigma^2}{2}

In words, the geometric mean is roughly the arithmetic mean minus half the variance.

Arithmetic and geometric returns

σp2=w12σ12+w22σ22+2w1w2ρσ1σ2\sigma_p^2 = w_1^2 \sigma_1^2 + w_2^2 \sigma_2^2 + 2 w_1 w_2 \rho \, \sigma_1 \sigma_2

In words, portfolio variance is each asset's weighted variance plus twice the weighted covariance between them.

Two-asset portfolio risk

SE=σn\text{SE} = \frac{\sigma}{\sqrt{n}}

In words, the standard error is the yearly standard deviation divided by the square root of the number of years.

The standard error of an average

Pr⁡(K=k)=n!k!(n−k)!pk(1−p)n−k\Pr(K = k) = \frac{n!}{k! \, (n-k)!} \, p^{k} (1-p)^{n-k}

In words, the chance of k successes is the number of ways to choose which tries succeed, times the chance of k successes and n minus k failures in one such order.

Counting successes with the binomial

Pr⁡(R∣S)=Pr⁡(S∣R)Pr⁡(R)Pr⁡(S∣R)Pr⁡(R)+Pr⁡(S∣not R)Pr⁡(not R)\Pr(R \mid S) = \frac{\Pr(S \mid R) \Pr(R)}{\Pr(S \mid R) \Pr(R) + \Pr(S \mid \text{not } R) \Pr(\text{not } R)}

In words, the chance of the event given the signal equals the chance of a true alarm divided by the chance of any alarm, true or false.

Bayes' rule and a recession signal

Chapter 4 · Time value of money and compounding

FV=PV(1+r)nFV = PV \, (1 + r)^{n}

In words, the future value equals today's sum multiplied by one plus the rate, once for every period.

Future and present value

PV=FV(1+r)nPV = \frac{FV}{(1 + r)^{n}}

In words, the present value equals the future sum divided by one plus the rate, once for every period.

Future and present value

PV=C1−(1+r)−nrPV = C \, \frac{1 - (1 + r)^{-n}}{r}

In words, the value of a level stream is the payment times one minus the discount factor for the last date, divided by the rate.

Annuities: a level stream of payments

PV=CrPV = \frac{C}{r}

In words, a level payment forever is worth the payment divided by the rate.

Perpetuities

PV=Cr−gPV = \frac{C}{r - g}

In words, a payment that grows at g forever is worth the first payment divided by the rate minus the growth rate.

Perpetuities

NPV=∑t=0nCFt(1+r)t\text{NPV} = \sum_{t=0}^{n} \frac{CF_t}{(1 + r)^{t}}

In words, net present value is the sum of every cash flow, each divided by one plus the discount rate once for every year until it arrives.

Net present value and internal rate of return

n=ln⁡(FV/PV)ln⁡(1+r)n = \frac{\ln(FV / PV)}{\ln(1 + r)}

In words, the number of years equals the log of the target over today's sum, divided by the log of one plus the rate.

Solving for time

1+i=(1+rreal)(1+π)1 + i = (1 + r_{\text{real}})(1 + \pi)

In words, one plus the nominal rate equals one plus the real rate times one plus inflation.

The Fisher relation exactly

Chapter 5 · Microeconomics: supply, demand, elasticity, market structure, moats

ε=%ΔQ%ΔP\varepsilon = \frac{\% \Delta Q}{\% \Delta P}

In words, the price elasticity of demand is the percentage change in quantity divided by the percentage change in price.

Price elasticity of demand

P−MCP=1|ε|\frac{P - MC}{P} = \frac{1}{|\varepsilon|}

In words, the share of the price that is markup over marginal cost equals one over the size of the demand elasticity the firm faces.

Pricing power and the markup

ΔPP≈s|εd|+εs\frac{\Delta P}{P} \approx \frac{s}{|\varepsilon_d| + \varepsilon_s}

In words, the price change is the size of the shift divided by the sum of how strongly buyers and sellers respond.

How far a shift moves the price

EP=(ROIC−WACC)×IC\text{EP} = (\text{ROIC} - \text{WACC}) \times \text{IC}

In words, economic profit is the return on invested capital minus the weighted average cost of capital, times the capital invested.

Economic profit

Vmoat=∑t=1Ts1(1−t−1T)IC(1+r)tV_{\text{moat}} = \sum_{t=1}^{T} \frac{s_1 \left( 1 - \frac{t-1}{T} \right) \text{IC}}{(1 + r)^{t}}

In words, the moat is worth the sum of each year's shrinking excess return on capital, discounted back to today.

The value of a moat

Chapter 6 · Macroeconomics: GDP, inflation, unemployment, the business cycle

1+greal=1+gnominal1+πdeflator1 + g_{\text{real}} = \frac{1 + g_{\text{nominal}}}{1 + \pi_{\text{deflator}}}

In words, one plus real growth equals one plus nominal growth divided by one plus the rise in the price deflator.

Real growth from nominal growth and the deflator

y≈−β(u−u∗)y \approx -\beta \, (u - u^{*})

In words, the output gap is about minus Okun's coefficient times the amount by which unemployment exceeds its natural rate.

Okun's coefficient

purchasing power=1(1+π)n\text{purchasing power} = \frac{1}{(1 + \pi)^{n}}

In words, after n years a dollar buys one divided by one plus inflation to the power n of what it bought at first.

What inflation does over time

Chapter 7 · Monetary and fiscal policy, the Taylor rule and the yield curve

i=r∗+π+0.5(π−π∗)+0.5yi = r^{*} + \pi + 0.5 \, (\pi - \pi^{*}) + 0.5 \, y

In words, the policy rate equals the neutral real rate plus inflation, plus half the gap between inflation and its target, plus half the output gap.

The Taylor rule

k=11−c(1−t)+mk = \frac{1}{1 - c(1 - t) + m}

In words, the multiplier is one over one minus the share of each dollar that is spent again at home.

The fiscal multiplier

dt+1=dt1+r1+g−pbd_{t+1} = d_t \, \frac{1 + r}{1 + g} - \text{pb}

In words, next year's debt ratio is this year's grown by one plus the interest rate over one plus the growth rate, minus the primary surplus.

Debt dynamics: the r minus g equation

Chapter 8 · Bonds and the maths of basis points

P=∑k=1NC(1+y/m)k+F(1+y/m)NP = \sum_{k=1}^{N} \frac{C}{(1 + y/m)^{k}} + \frac{F}{(1 + y/m)^{N}}

In words, a bond's price equals every coupon and the face value added up, each one divided by one plus the period yield once for every period until it arrives.

Pricing a bond

Dmac=1P∑k=1NtkCFk(1+y/m)kD_{\text{mac}} = \frac{1}{P} \sum_{k=1}^{N} t_k \, \frac{CF_k}{(1 + y/m)^{k}}

In words, Macaulay duration is the average time until the bond's cash arrives, with each date weighted by the present value of the payment due then.

Macaulay and modified duration

Dmod=Dmac1+y/m=−1P∂P∂yD_{\text{mod}} = \frac{D_{\text{mac}}}{1 + y/m} = -\frac{1}{P} \frac{\partial P}{\partial y}

In words, modified duration is Macaulay duration divided by one plus the period yield, and it equals the percentage fall in price for each unit rise in the yield.

Macaulay and modified duration

C=1P∂2P∂y2C = \frac{1}{P} \frac{\partial^{2} P}{\partial y^{2}}

In words, convexity measures how fast duration itself changes as the yield moves, per dollar of price.

Convexity and the second-order estimate

ΔPP≈−DmodΔy+12C(Δy)2\frac{\Delta P}{P} \approx -D_{\text{mod}} \, \Delta y + \tfrac12 \, C \, (\Delta y)^{2}

In words, the percentage price change is about minus duration times the yield change, plus half the convexity times the yield change squared.

Convexity and the second-order estimate

DV01=P×Dmod×0.0001\text{DV01} = P \times D_{\text{mod}} \times 0.0001

In words, DV01 is the market value of the holding times its modified duration times one basis point, the dollar change for a 0.01 percentage point move in yield.

DV01: one basis point in dollars

1+i=(1+r)(1+π)1 + i = (1 + r)(1 + \pi)

In words, one plus the nominal rate equals one plus the real rate times one plus inflation.

Breakeven inflation and the Fisher relation

TEY=ymuni1−t\text{TEY} = \frac{y_{\text{muni}}}{1 - t}

In words, the taxable-equivalent yield is the tax-free yield divided by one minus the investor's tax rate.

Breakeven inflation and the Fisher relation

Chapter 9 · Credit: corporate bonds, munis, ratings, spreads, default and recovery

EL=PD×LGD×EAD\text{EL} = \text{PD} \times \text{LGD} \times \text{EAD}

In words, expected loss equals the probability of default times the loss given default times the exposure at default.

Expected loss

s≈PD×LGD+ϕs \approx \text{PD} \times \text{LGD} + \phi

In words, a credit spread is roughly the yearly expected loss rate plus a premium for bearing default risk and illiquidity.

Spread as expected loss plus premium

PD∗=s1−R\text{PD}^{*} = \frac{s}{1 - R}

In words, the breakeven default rate is the spread divided by one minus the recovery rate.

The breakeven default rate

S(n)=(1−p)nCDR(n)=1−(1−p)nS(n) = (1 - p)^{n} \qquad \text{CDR}(n) = 1 - (1 - p)^{n}

In words, the chance of no default for n years is one minus the yearly rate, multiplied by itself n times, and the cumulative default rate is one minus that.

Cumulative default and survival

Chapter 10 · Equity valuation

P0=D1r−gP_0 = \frac{D_1}{r - g}

In words, the value of a share equals next year's dividend divided by the gap between the required return and the growth rate.

The Gordon growth model

P0E1=br−g\frac{P_0}{E_1} = \frac{b}{r - g}

In words, a justified forward P/E equals the payout ratio divided by the gap between the required return and growth.

Justified P/E and the earnings yield

V0=E1(1−g/ROIC)r−gV_0 = \frac{E_1 \left( 1 - g / \text{ROIC} \right)}{r - g}

In words, a firm's value equals next year's earnings, less the share it must reinvest to grow, divided by the gap between the required return and growth.

Growth, ROIC and the value of a moat

WACC=ED+ErE+DD+ErD(1−t)\text{WACC} = \frac{E}{D + E} \, r_E + \frac{D}{D + E} \, r_D \, (1 - t)

In words, the weighted average cost of capital is the cost of equity times the equity share plus the after-tax cost of debt times the debt share.

The cost of capital

E[r]=D1P0+g\mathbb{E}[r] = \frac{D_1}{P_0} + g

In words, the return a buyer can expect over the long run equals the dividend yield plus the growth rate of dividends.

The return a price implies

V0=∑t=1TFCFt(1+WACC)t+TVT(1+WACC)TTVT=FCFT+1WACC−gV_0 = \sum_{t=1}^{T} \frac{\text{FCF}_t}{(1 + \text{WACC})^{t}} + \frac{\text{TV}_T}{(1 + \text{WACC})^{T}} \qquad \text{TV}_T = \frac{\text{FCF}_{T+1}}{\text{WACC} - g}

In words, the value of a business equals each forecast year's free cash flow discounted at the WACC, plus a terminal value for the years beyond, itself a Gordon value discounted back from the end of the forecast.

A five-year discounted cash flow

Chapter 11 · Equity risk drivers, factors, international and emerging markets

E[Ri]=rf+βi(E[Rm]−rf)\mathbb{E}[R_i] = r_f + \beta_i \left( \mathbb{E}[R_m] - r_f \right)

In words, a stock's expected return equals the risk-free rate plus its beta times the market's premium over the risk-free rate.

The capital asset pricing model

βi=Cov(Ri,Rm)Var(Rm)=ρi,mσiσm\beta_i = \frac{\text{Cov}(R_i, R_m)}{\text{Var}(R_m)} = \rho_{i,m} \, \frac{\sigma_i}{\sigma_m}

In words, beta equals the stock's correlation with the market times its volatility divided by the market's volatility.

Beta from covariance

E[Ri]=rf+biMRP+siSMB+hiHML\mathbb{E}[R_i] = r_f + b_i \, \text{MRP} + s_i \, \text{SMB} + h_i \, \text{HML}

In words, expected return equals the risk-free rate plus the stock's exposure to each factor times that factor's premium, summed over the market, size and value factors.

Multi-factor models

σp=ρσ2+(1−ρ)σ2n\sigma_p = \sqrt{\rho \, \sigma^{2} + \frac{(1 - \rho) \, \sigma^{2}}{n}}

In words, the portfolio's volatility is the square root of the shared part of the variance, which stays, plus the company-specific part divided by the number of stocks.

How many stocks it takes to diversify

1+R$=(1+RL)(1+RFX)1 + R_{\$} = (1 + R_L)(1 + R_{FX})

In words, one plus the dollar return equals one plus the local return times one plus the currency return.

Dollar return of a foreign stock

Chapter 12 · Real estate and REITs

V=NOIcV = \frac{\text{NOI}}{c}

In words, a property's value equals its net operating income divided by the cap rate.

Cap rate valuation

c=r−gc = r - g

In words, a cap rate equals the total return buyers require less the growth rate they expect for the building's income.

The cap rate as a required return less growth

ΔEE=ΔVV×VV−D\frac{\Delta E}{E} = \frac{\Delta V}{V} \times \frac{V}{V - D}

In words, the percentage change in the investor's equity equals the percentage change in the property's value times the value divided by the equity.

Leverage and the equity holder

Chapter 13 · Commodities and gold

F=Se(r+u−y)TF = S \, e^{(r + u - y) T}

In words, the futures price equals the spot price grown at the interest rate plus the storage cost, less the benefit of holding the good, over the time to delivery.

Cost of carry

roll yield=Fnear−FnextFnear\text{roll yield} = \frac{F_{\text{near}} - F_{\text{next}}}{F_{\text{near}}}

In words, the roll yield is the gap between the expiring price and the next contract's price, as a share of the expiring price.

Roll yield in numbers

Chapter 14 · Currencies and what moves them

F=S1+id1+ifF = S \, \frac{1 + i_d}{1 + i_f}

In words, the forward rate equals the spot rate times one plus the home interest rate, divided by one plus the foreign interest rate.

Covered interest parity

SnS0=(1+πd1+πf)n\frac{S_{n}}{S_{0}} = \left( \frac{1 + \pi_d}{1 + \pi_f} \right)^{n}

In words, over nn years the dollar price of a foreign currency should rise by the ratio of home to foreign inflation, compounded.

Purchasing power parity and the real exchange rate

Chapter 15 · Forwards, futures and swaps

F0=S0e(r−q)TF_{0} = S_{0} \, e^{(r - q) T}

In words, the forward price is the spot price grown at the risk-free rate less the income the asset pays, for the time to delivery.

Forward pricing

h∗=ρσSσFh^{*} = \rho \, \frac{\sigma_{S}}{\sigma_{F}}

In words, the best hedge ratio is the correlation between the two prices times the ratio of their volatilities.

The minimum-variance hedge ratio

s=1−Dn∑t=1nDts = \frac{1 - D_{n}}{\sum_{t=1}^{n} D_{t}}

In words, the par swap rate equals one minus the final discount factor, divided by the sum of all the discount factors.

A swap as two bonds

Chapter 16 · Options: European, American, Bermudan and exotics; binomial, Black–Scholes, the Greeks

C−P=S0−Ke−rTC - P = S_{0} - K \, e^{-rT}

In words, a call minus a put with the same strike and expiry is worth the share price minus the strike discounted at the risk-free rate.

Put-call parity

q=erΔt−du−dq = \frac{e^{r \Delta t} - d}{u - d}

In words, qq is the probability that makes the share's expected growth equal the risk-free rate.

One-step binomial

C=S0N(d1)−Ke−rTN(d2)C = S_{0} \, N(d_{1}) - K e^{-rT} N(d_{2})

In words, the call is worth the share price times one probability-like factor, minus the discounted strike times another.

Black–Scholes

P=Ke−rTN(−d2)−S0N(−d1)P = K e^{-rT} N(-d_{2}) - S_{0} \, N(-d_{1})

In words, the put is worth the discounted strike times the chance of ending in the money, minus the share price times the put's share-equivalent.

Black–Scholes

Θ+12σ2S2Γ+rSΔ=rV\Theta + \tfrac12 \sigma^{2} S^{2} \Gamma + r S \Delta = r V

In words, the time decay plus the gain from curvature plus the interest on the hedge equals the risk-free return on the option's value.

The Greeks

σday=VIX252\sigma_{\text{day}} = \frac{\text{VIX}}{\sqrt{252}}

In words, the daily standard deviation the options imply is the VIX divided by the square root of 252.

Reading the VIX as a daily move

Chapter 17 · Credit derivatives and structured products: CDS, MBS, ABS, CDOs, tranching and 2008

Q(t)=e−λtQ(t) = e^{-\lambda t}

In words, the chance the borrower is still paying at time tt is the exponential of minus the hazard rate times tt.

Hazard rates and survival

s≈λ(1−R)⇒λ≈s1−Rs \approx \lambda \, (1 - R) \quad \Rightarrow \quad \lambda \approx \frac{s}{1 - R}

In words, the CDS spread is about the hazard rate times the loss given default, so the hazard rate is about the spread divided by one minus the recovery rate.

The credit triangle

PVprem=sNA,PVprot=(1−R)NλA\text{PV}_{\text{prem}} = s \, N A, \quad \text{PV}_{\text{prot}} = (1 - R) \, N \lambda A

In words, the premium leg equals spread times notional times the risky annuity, and the protection leg is the loss given default times the notional times the hazard rate times the same annuity.

Pricing both legs

tranche loss=min⁡(max⁡(L−a,0),d−a)d−a\text{tranche loss} = \frac{\min(\max(L - a, 0), \, d - a)}{d - a}

In words, a tranche loses nothing until pool losses reach its attachment point, then loses every further dollar until its detachment point, measured as a share of its thickness.

Tranche loss arithmetic

p(M)=N(N−1(p)−ρM1−ρ)p(M) = N\left( \frac{N^{-1}(p) - \sqrt{\rho} \, M}{\sqrt{1 - \rho}} \right)

In words, in a bad state of the economy (low MM) the default rate rises above its average, and the correlation ρ\rho sets how far it swings with the economy.

Correlation in the one-factor model

Chapter 18 · Portfolio construction: MPT, the efficient frontier, CAPM, factors, rebalancing

E[Rp]=wSμS+wBμB\mathbb{E}[R_p] = w_S \mu_S + w_B \mu_B

In words, the portfolio's expected return is each asset's expected return times its weight, added up.

Two assets: return and risk

σp2=wS2σS2+wB2σB2+2wSwBρσSσB\sigma_p^2 = w_S^2 \sigma_S^2 + w_B^2 \sigma_B^2 + 2 w_S w_B \rho \sigma_S \sigma_B

In words, the portfolio's variance is each asset's variance times its weight squared, plus twice the product of the weights, the correlation and the two standard deviations.

Two assets: return and risk

wSmin⁡=σB2−ρσSσBσS2+σB2−2ρσSσBw_S^{\min} = \frac{\sigma_B^2 - \rho \sigma_S \sigma_B}{\sigma_S^2 + \sigma_B^2 - 2 \rho \sigma_S \sigma_B}

In words, the least-risk stock weight is the bond variance less the covariance, over the sum of both variances less twice the covariance.

The minimum-variance mix

wS∗=(μS−rf)σB2−(μB−rf)ρσSσB(μS−rf)σB2+(μB−rf)σS2−(μS+μB−2rf)ρσSσBw_S^{*} = \frac{(\mu_S - r_f)\sigma_B^2 - (\mu_B - r_f)\rho \sigma_S \sigma_B}{(\mu_S - r_f)\sigma_B^2 + (\mu_B - r_f)\sigma_S^2 - (\mu_S + \mu_B - 2 r_f)\rho \sigma_S \sigma_B}

In words, the tangency stock weight trades each asset's excess return against its variance and the covariance between the two.

The tangency portfolio and the capital market line

E[Rp]=rf+E[RT]−rfσTσp\mathbb{E}[R_p] = r_f + \frac{\mathbb{E}[R_T] - r_f}{\sigma_T}\,\sigma_p

In words, on the capital market line each unit of standard deviation earns the tangency portfolio's Sharpe ratio on top of the bill rate.

The tangency portfolio and the capital market line

y∗=E[RT]−rfAσT2y^{*} = \frac{\mathbb{E}[R_T] - r_f}{A\,\sigma_T^2}

In words, the best share in the risky portfolio is its excess return divided by the investor's risk aversion times the risky portfolio's variance.

The tangency portfolio and the capital market line

σp2=σ2n+(1−1n)ρσ2\sigma_p^2 = \frac{\sigma^2}{n} + \left(1 - \frac{1}{n}\right)\rho \sigma^2

In words, the variance is one asset's variance divided by the number of assets, plus a share of the common covariance that does not shrink as assets are added.

Many assets: what diversification can and cannot remove

RCS=wS(wSσS2+wBρσSσB)σp2\text{RC}_S = \frac{w_S\left(w_S \sigma_S^2 + w_B \rho \sigma_S \sigma_B\right)}{\sigma_p^2}

In words, the stock share of risk is the stock weight times the stock's covariance with the portfolio, divided by the portfolio's variance.

Risk contributions and risk parity

DR≈12(∑iwiσi2−σp2)\text{DR} \approx \tfrac12 \left( \sum_i w_i \sigma_i^2 - \sigma_p^2 \right)

In words, the extra growth from rebalancing is half the gap between the weighted average of the assets' variances and the portfolio's own variance.

Rebalancing and the diversification return

wS(n)=wS(1+rS)nwS(1+rS)n+wB(1+rB)nw_S^{(n)} = \frac{w_S (1 + r_S)^n}{w_S (1 + r_S)^n + w_B (1 + r_B)^n}

In words, the new stock weight is the grown stock value divided by the grown value of everything.

Drift and the rebalancing trade

E[Ri]=rf+βi(E[Rm]−rf)\mathbb{E}[R_i] = r_f + \beta_i \left(\mathbb{E}[R_m] - r_f\right)

In words, an asset's required return is the bill rate plus its beta times the market's premium over bills.

CAPM and the performance measures

Chapter 19 · Behavioural finance

v(x)=xαfor x≥0,v(x)=−λ(−x)βfor x<0v(x) = x^{\alpha} \text{ for } x \ge 0, \qquad v(x) = -\lambda (-x)^{\beta} \text{ for } x < 0

In words, a gain's felt value is the gain raised to a power below one, and a loss's felt value is minus the loss-aversion coefficient times the loss raised to a power below one.

The value function

w(p)=pγ(pγ+(1−p)γ)1/γw(p) = \frac{p^{\gamma}}{\left(p^{\gamma} + (1 - p)^{\gamma}\right)^{1/\gamma}}

In words, the decision weight of a chance is the chance raised to a power, divided by a scaling term that keeps the weights between zero and one.

Probability weighting and lottery-like assets

g=((1+r)nPE0PEn)1/n−1g = \left( (1 + r)^{n} \frac{\text{PE}_0}{\text{PE}_n} \right)^{1/n} - 1

In words, the growth needed is the required return compounded over the years, times the fall in the multiple, taken to the root of the number of years, less one.

What a bubble price asks of the future

Chapter 20 · The 11 asset classes, deepened: risk drivers and one example per driver

P1P0−1=r0−g0r1−g1−1\frac{P_1}{P_0} - 1 = \frac{r_0 - g_0}{r_1 - g_1} - 1

In words, the percentage change in price equals the old gap between return and growth divided by the new gap, minus one.

One equation per class

1+RUSD=(1+Rlocal)(1+RFX)1 + R_{\text{USD}} = (1 + R_{\text{local}})(1 + R_{\text{FX}})

In words, one plus the dollar return equals one plus the local return times one plus the currency's change against the dollar.

One equation per class

TEY=ymuni1−t\text{TEY} = \frac{y_{\text{muni}}}{1 - t}

In words, the taxable-equivalent yield is the muni yield divided by one minus the buyer's tax rate.

One equation per class

RTIPS≈πaccrual+r−DrealΔrR_{\text{TIPS}} \approx \pi_{\text{accrual}} + r - D_{\text{real}} \, \Delta r

In words, a TIPS bond earns the inflation added to its principal and its real coupon, and loses its real duration times any rise in the real yield.

One equation per class

ΔEE=ΔV/V1−LTV\frac{\Delta E}{E} = \frac{\Delta V / V}{1 - \text{LTV}}

In words, the percentage change in equity equals the percentage change in property value divided by one minus the loan-to-value ratio.

One equation per class

Rfutures≈ΔS+roll+rcollateralR_{\text{futures}} \approx \Delta S + \text{roll} + r_{\text{collateral}}

In words, a futures investor earns the change in the spot price plus the roll yield plus the interest on the cash held as collateral.

One equation per class

Preal=Pnominal×CPInowCPIthenP_{\text{real}} = P_{\text{nominal}} \times \frac{\text{CPI}_{\text{now}}}{\text{CPI}_{\text{then}}}

In words, a past price in today's money equals the past price times today's CPI divided by the CPI at the time.

One equation per class

Rcarry=(1+iinvest)(1+Δs)−(1+ifund)R_{\text{carry}} = (1 + i_{\text{invest}})(1 + \Delta s) - (1 + i_{\text{fund}})

In words, the carry return equals the grown value of the investment, after the currency move, minus what the borrowed money costs to repay.

One equation per class

Chapter 21 · Fiduciary duty, advisers vs brokers, the regulators

Vn=V0(1+g−f)nV_{n} = V_{0} \, (1 + g - f)^{n}

In words, the value after nn years equals the starting value grown at the gross return less the fee, once for each year.

Fee drag over twenty years

n∗=ln⁡(1−L)ln⁡(1+g−f1+g)n^{*} = \frac{\ln(1 - L)}{\ln\left(\frac{1 + g - f}{1 + g}\right)}

In words, the break-even holding period is the log of what the load leaves you divided by the log of the yearly fee's growth penalty.

A one-time load against a yearly fee

Chapter 22 · Accounts, taxes and the investor's plan

drag=y×t\text{drag} = y \times t

In words, the return lost to tax each year equals the yield multiplied by the tax rate on it.

Asset location drag

TEY=ymuni1−t\text{TEY} = \frac{y_{\text{muni}}}{1 - t}

In words, the taxable-equivalent yield is the tax-free yield divided by one minus the investor's tax rate.

Muni or taxable: the taxable-equivalent yield

WRoth=(1−tc)(1+r)nW_{\text{Roth}} = (1 - t_{c}) \, (1 + r)^{n}

In words, the Roth's value is the dollar after today's tax, grown untaxed.

Roth or traditional: the break-even tax rate

PV=Ltnow−Ltlater(1+d)T\text{PV} = L \, t_{\text{now}} - \frac{L \, t_{\text{later}}}{(1 + d)^{T}}

In words, the value of a harvest is the tax saved today less today's value of the extra tax due when the investor sells the lower-basis shares.

What a harvested loss is worth

1+R=(1+s)(1+π)1 + R = (1 + s)(1 + \pi)

In words, one plus the required return equals one plus the spending rate times one plus inflation.

A required return for the policy statement

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