If you invested $100 in the S&P 500 at the beginning of 1980, you would have about $464.51 at the end of 1989, assuming you reinvested all dividends. This is a return on investment of 364.51%, or 16.60% per year.
This lump-sum investment beats inflation during this period for an inflation-adjusted return of about 208.67% cumulatively, or 11.93% per year.
If you used dollar-cost averaging (monthly) instead of a lump-sum investment, you'd have $399.53.
The graph below shows the performance of $100 over time if invested in an S&P 500 index fund. The returns assume that all dividends are automatically reinvested.
The nominal return on investment of $100 is $364.51, or 364.51%. This means by 1989 you would have $464.51 in your pocket.
However, it's important to take into account the effect of inflation when considering an investment and especially a long-term investment. You can convert S&P returns to their real (inflation-adjusted) value using an inflation calculation based on the U.S. Bureau of Labor Statistics Consumer Price Index (CPI).
In the case of the returns described above, the CPI in 1980 was 82.400 and the CPI in 1989 was 124.000.
The ratio between these CPIs describes how relative buying power of a dollar has changed over 9 years.
Adjusted for inflation, the $464.51 nominal end value of the original $100 investment would have a real return of roughly $208.67 in 1980 dollars. This means the inflation-adjusted return is 208.67% as opposed to the original 364.51%.
The table below shows the full dataset pertaining to a $100 investment, including gains and losses over the 120-month period between 1980 and 1989.
Note that data shown is the monthly average closing price. Returns include dividends.
Year
Month
Return (%)
Amount ($)
CPI
1980
1
4.40%
104.40
77.80
1980
2
-8.78%
95.23
78.90
1980
3
-1.16%
94.13
80.10
1980
4
5.04%
98.87
81.00
1980
5
6.86%
105.65
81.80
1980
6
4.97%
110.90
82.70
1980
7
3.50%
114.79
82.70
1980
8
2.84%
118.04
83.30
1980
9
3.32%
121.97
84.00
1980
10
4.61%
127.60
84.80
1980
11
-1.24%
126.01
85.50
1980
12
0.01%
126.02
86.30
1981
1
-3.07%
122.15
87.00
1981
2
4.14%
127.21
87.90
1981
3
1.29%
128.86
88.50
1981
4
-1.62%
126.77
89.10
1981
5
0.86%
127.86
89.80
1981
6
-2.02%
125.28
90.60
1981
7
0.80%
126.29
91.60
1981
8
-8.30%
115.80
92.30
1981
9
1.73%
117.80
93.20
1981
10
3.04%
121.39
93.40
1981
11
1.18%
122.82
93.70
1981
12
-4.80%
116.92
94.00
1982
1
-1.91%
114.68
94.30
1982
2
-2.74%
111.54
94.60
1982
3
5.47%
117.64
94.50
1982
4
0.57%
118.31
94.90
1982
5
-5.27%
112.07
95.80
1982
6
0.24%
112.34
97.00
1982
7
0.79%
113.24
97.50
1982
8
12.10%
126.93
97.70
1982
9
8.88%
138.21
97.90
1982
10
4.50%
144.43
98.20
1982
11
1.36%
146.38
98.00
1982
12
3.93%
152.13
97.60
1983
1
2.13%
155.37
97.80
1983
2
3.87%
161.38
97.90
1983
3
4.20%
168.15
97.90
1983
4
4.42%
175.59
98.60
1983
5
1.75%
178.67
99.20
1983
6
0.71%
179.93
99.50
1983
7
-2.41%
175.60
99.90
1983
8
3.31%
181.42
100.20
1983
9
0.65%
182.60
100.70
1983
10
-1.14%
180.51
101.00
1983
11
-0.13%
180.28
101.20
1983
12
1.58%
183.12
101.30
1984
1
-5.11%
173.76
101.90
1984
2
0.44%
174.53
102.40
1984
3
0.51%
175.41
102.60
1984
4
-0.25%
174.97
103.10
1984
5
-1.85%
171.74
103.40
1984
6
-0.91%
170.18
103.70
1984
7
9.21%
185.84
104.10
1984
8
1.41%
188.46
104.50
1984
9
-0.41%
187.68
105.00
1984
10
1.29%
190.10
105.30
1984
11
-0.71%
188.75
105.30
1984
12
4.70%
197.62
105.30
1985
1
5.79%
209.05
105.50
1985
2
-0.48%
208.05
106.00
1985
3
1.02%
210.19
106.40
1985
4
2.74%
215.94
106.90
1985
5
2.51%
221.36
107.30
1985
6
2.25%
226.33
107.60
1985
7
-1.85%
222.16
107.80
1985
8
-1.88%
217.97
108.00
1985
9
1.50%
221.23
108.30
1985
10
6.42%
235.43
108.70
1985
11
5.29%
247.90
109.00
1985
12
0.75%
249.76
109.30
1986
1
5.70%
263.99
109.60
1986
2
6.18%
280.31
109.30
1986
3
2.74%
288.00
108.80
1986
4
0.49%
289.41
108.60
1986
5
3.13%
298.48
108.90
1986
6
-1.80%
293.10
109.50
1986
7
2.28%
299.78
109.50
1986
8
-2.46%
292.42
109.70
1986
9
-0.09%
292.15
110.20
1986
10
3.53%
302.48
110.30
1986
11
1.71%
307.65
110.40
1986
12
6.67%
328.18
110.50
1987
1
6.46%
349.38
111.20
1987
2
4.38%
364.67
111.60
1987
3
-0.86%
361.55
112.10
1987
4
0.17%
362.17
112.70
1987
5
4.50%
378.47
113.10
1987
6
3.12%
390.28
113.50
1987
7
6.45%
415.47
113.80
1987
8
-3.03%
402.88
114.40
1987
9
-11.85%
355.12
115.00
1987
10
-12.30%
311.43
115.30
1987
11
-1.33%
307.28
115.40
1987
12
4.25%
320.32
115.40
1988
1
3.33%
330.99
115.70
1988
2
3.23%
341.68
116.00
1988
3
-0.89%
338.66
116.50
1988
4
-2.19%
331.25
117.10
1988
5
6.00%
351.11
117.50
1988
6
-0.31%
350.04
118.00
1988
7
-1.72%
344.02
118.50
1988
8
1.93%
350.65
119.00
1988
9
3.80%
363.98
119.80
1988
10
-2.02%
356.63
120.20
1988
11
2.33%
364.92
120.30
1988
12
3.51%
377.74
120.50
1989
1
3.30%
390.21
121.10
1989
2
-0.16%
389.58
121.60
1989
3
3.56%
403.46
122.30
1989
4
4.12%
420.07
123.10
1989
5
3.39%
434.32
123.80
1989
6
2.80%
446.48
124.10
1989
7
4.69%
467.42
124.40
1989
8
0.46%
469.55
124.60
1989
9
0.29%
470.90
125.00
1989
10
-1.81%
462.36
125.60
1989
11
2.74%
475.01
125.90
1989
12
-2.21%
464.51
126.10
Click to show 102 more rows
Remember, returns are based on the average closing price across the entire month. Some losses are offset by dividend returns.
Dollar-cost averaging
Dollar-cost averaging is an alternative to investing the full lump-sum of $100.00 up-front. Instead, the capital is invested over a period of time.
Consider a strategy in which $100.00 was invested in the S&P 500 over a period of no more than 24 months beginning in 1980. This would result in a final amount of $399.53, including dividend reinvestments. In this particular case, dollar-cost average returns are less than the returns of a lump-sum investment (which ends with $464.51).
Year
Month
Contribution ($)
Amount ($)
1980
1
4.16
4.33
1980
2
4.16
7.72
1980
3
4.16
11.73
1980
4
4.16
16.67
1980
5
4.16
22.24
1980
6
4.16
27.69
1980
7
4.16
32.95
1980
8
4.16
38.14
1980
9
4.16
43.69
1980
10
4.16
50.05
1980
11
4.16
53.52
1980
12
4.16
57.67
1981
1
4.16
59.91
1981
2
4.16
66.71
1981
3
4.16
71.77
1981
4
4.16
74.69
1981
5
4.16
79.50
1981
6
4.16
81.96
1981
7
4.16
86.80
1981
8
4.16
83.39
1981
9
4.16
89.04
1981
10
4.16
96.02
1981
11
4.16
101.34
1981
12
4.32
100.56
1982
1
-
98.64
1982
2
-
95.93
1982
3
-
101.18
1982
4
-
101.76
1982
5
-
96.39
1982
6
-
96.63
1982
7
-
97.39
1982
8
-
109.18
1982
9
-
118.87
1982
10
-
124.22
1982
11
-
125.91
1982
12
-
130.85
1983
1
-
133.64
1983
2
-
138.80
1983
3
-
144.63
1983
4
-
151.03
1983
5
-
153.67
1983
6
-
154.76
1983
7
-
151.04
1983
8
-
156.04
1983
9
-
157.05
1983
10
-
155.26
1983
11
-
155.06
1983
12
-
157.50
1984
1
-
149.45
1984
2
-
150.11
1984
3
-
150.88
1984
4
-
150.49
1984
5
-
147.71
1984
6
-
146.37
1984
7
-
159.85
1984
8
-
162.10
1984
9
-
161.43
1984
10
-
163.50
1984
11
-
162.35
1984
12
-
169.97
1985
1
-
179.81
1985
2
-
178.95
1985
3
-
180.78
1985
4
-
185.73
1985
5
-
190.39
1985
6
-
194.67
1985
7
-
191.08
1985
8
-
187.48
1985
9
-
190.28
1985
10
-
202.50
1985
11
-
213.22
1985
12
-
214.82
1986
1
-
227.06
1986
2
-
241.10
1986
3
-
247.71
1986
4
-
248.93
1986
5
-
256.73
1986
6
-
252.10
1986
7
-
257.84
1986
8
-
251.51
1986
9
-
251.29
1986
10
-
260.16
1986
11
-
264.61
1986
12
-
282.27
1987
1
-
300.51
1987
2
-
313.66
1987
3
-
310.97
1987
4
-
311.51
1987
5
-
325.52
1987
6
-
335.69
1987
7
-
357.35
1987
8
-
346.52
1987
9
-
305.45
1987
10
-
267.87
1987
11
-
264.29
1987
12
-
275.51
1988
1
-
284.68
1988
2
-
293.89
1988
3
-
291.28
1988
4
-
284.91
1988
5
-
302.00
1988
6
-
301.07
1988
7
-
295.90
1988
8
-
301.60
1988
9
-
313.06
1988
10
-
306.74
1988
11
-
313.87
1988
12
-
324.90
1989
1
-
335.62
1989
2
-
335.08
1989
3
-
347.02
1989
4
-
361.30
1989
5
-
373.56
1989
6
-
384.02
1989
7
-
402.04
1989
8
-
403.87
1989
9
-
405.02
1989
10
-
397.68
1989
11
-
408.56
1989
12
-
399.53
Click to show 102 more rows
Data Sources
The information on this page is derived from Robert Shiller's book, Irrational Exuberance and the accompanying dataset, as well as the U.S. Bureau of Labor Statistics' monthly CPI logs.
Note that S&P index value for the current quarter is based on a moving average of closing prices, per Robert Shiller's methodology. The inflation data used is based on annual CPI averages.
About the author
Ian Webster is an engineer and data expert based in San Mateo, California. He has worked for Google, NASA, and consulted for governments around the world on data pipelines and data analysis. Disappointed by the lack of clear resources on the impacts of inflation on economic indicators, Ian believes this website serves as a valuable public tool. Ian earned his degree in Computer Science from Dartmouth College.
