Natural logs are frequently used in finance.
ROW/COL B C D E F G H I
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7 The compound value of a $ is:
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9 V = P *(1+ i/n)^(n*t)
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14 where:
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16 V is the ending value
17 P is the present value you start with
18 I is the rate of interest
19 n is the frequency of compounding
20 t is the length of time
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22 Notice that part of the formula looks a lot like the expansion to get the value of "e"
23 If we let P=1 and t=1 it is exactly the same formula.
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25 V = 1 *(1+ i/n)^(n*1)
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30 If n =1 then we get:  (which is frequently the form of the compound amount formula)
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32 V = P *(1+ i/1)^(1*t)
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36 Impact of compounding
37 Using an interest rate of: 5.0000%
38 Assume the time period is 1 year and the amount is $1
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40 Frequency of compounding n V Annual Rate of return ln(Annual Rate of Return)
41 Annual 1 $1.05000 5.0000% 4.8790%
42 Semi-Annual 2 $1.05063 5.0625% 4.9385%
43 Quarterly 4 $1.05095 5.0945% 4.9690%
44 Monthly 12 $1.05116 5.1162% 4.9896%
45 Daily 365 $1.05127 5.1267% 4.9997%
46 Hourly 8760 $1.05127 5.1271% 5.0000%
47 Minutely 525600 $1.05127 5.1271% 5.0000%
48 Secondly 31536000 $1.05127 5.1271% 5.0000%
49 Infinite =EXP(i) $1.05127 5.1271% 5.0000%
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51 Notice that as the frequency of compounding increase our rate of return increase, but at a decreasing rate.
52 Until the difference between daily, secondly and infinite is nil.
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55 So if you allow infinite compounding the future value of a dollar formula becomes:
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57 V = P*exp(i*t)
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62 Remembering that ln and e^x are opposite transactions we can determine an equivalence between rates of interest and compounding
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65 You would indifferent between the following rates compounded once a year, or the rates compounded continuously.
66 Compounded once a year Compounded continuously Compound amount of $1 at the end of a year
67 Annual Rate of return ln(1+Annual Rate of Return) Once a year Continuously
68 5.0000% 4.8790% $1.0500 $1.0500
69 5.0625% 4.9385% $1.0506 $1.0506
70 5.0945% 4.9690% $1.0509 $1.0509
71 5.1162% 4.9896% $1.0512 $1.0512
72 5.1267% 4.9997% $1.0513 $1.0513
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5.1271%
5.0000% $1.0513 $1.0513
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75 You can always find a rate that will cause you to be indifferent between an annual rate and continuously compounded one by taking the ln(1+i)
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77 Annual Rate Continuously Compounded
78 5.0000% 4.8790% <=LN(1+B78)
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80 Or you find a continuously compounded rate that is equal to an annual rate by using exp(i)-1
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82 Continuously Compounded Annual Rate
83 5.5000% 5.6541% <=EXP(B83)-1
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85 Try it by changing the green numbers
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88 In many cases theoretical consideration require that we use continuously compounded rates in finance.
89 In general when using the CAPM and Black/Scholes you should use continuously compounded rates.
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