II2 VALUATION, DEPRECIATION AND THE RATE-BASE 
of which have a probable life of # years, after the plant is » 
years older than any of these parts, will be about one nth of 
their replacement cost. 
In a plant which continues to grow, the theoretical annual 
replacement requirement will gradually approach but can never 
quite reach one nth of the total replacement cost. (See Tables 
4 to 6.) 
TABLE 4. REPLACEMENT REQUIREMENTS 
NUMEROUS ARTICLES. PROBABLE LIFE 5 YEARS 
Each article is replaced as it goes out of use. For an original investment 
of $100 with no betterments or additions. Also for an investment growing 
at the uniform rate of $100 per year. 
(For the special hypothesis as stated in the text.) 
Plant of full growth, 
otigtanl Jioesiment Growing plant, annual investment $100. 
100. 
Replacements per year. Replacements per year.| Rerlyenients Por $100 
$ 4.00 $ 4.00 $ 4.00 
8.16 12.16 6.08 
12.65 24.81 8.27 
17.64 42.45 10.61 
23.34 65.78 13.16 
21.07 87.75 14.62 
21.16 108.91 15.56 
20.54 129.45 16.18 
19.73 149.18 16.58 
Lo 18.31 167.49 16.75 
II 19.73 187.22 17.02 
12 20.37 207.60 17.30 
1; 20.45 228.05 17.54 
20.21 248.25 7-73 
wr 19.90 268.16 17.88 
16 19.87 288.03 18.00 
2h 19.01 307.94 18.11 
¥3 20.03 327.92 33.22 
ia 20.06 347.95 18.31 
20 20.02 368.00 18.40 
21 20.00 388.02 18.48 
22 20.00 408.00 18.55 
27 20.00 428.00 18.61 
24 20.00 448.00 18.67 
23 20.00 468 .00 18.472 
Vear