Simple python program using while loops, off by one error - python-3.x

Question

I have tried to figure out where the off by one error is and have had no luck. I am an absolute beginner at programming. The increase is supposed to start on year two, but my code adds it to year one. Thanks in advance for any and all help!
##
# salaryschedule.py
# 2/15/2017
# This program will calculate and print the salary schedule for years 1
# through 30 for the teachers in Murdock County. For each year of
# experience, up to 20 years, the salary is increased by 2%.
# Each year after 20, the salary stays the same as year 20.
##
RATE = 2.0
INITIAL_SALARY = 37238.00
salary = INITIAL_SALARY
year = 1
print("Murdock County")
print("Teacher Salary Schedule")
print()
print("Year Salary")
print("---- ------")
while year < 31 :
increase = salary * RATE / 100
salary = salary + increase
print("%4d %15.2f" % (year, salary))
year = year + 1

Answer 1

You only have to print the salary before increasing it.
RATE = 2.0
INITIAL_SALARY = 37238.00
salary = INITIAL_SALARY
year = 1
print("Murdock County")
print("Teacher Salary Schedule")
print()
print("Year Salary")
print("---- ------")
while year < 31 :
print("%4d %15.2f" % (year, salary))
increase = salary * RATE / 100
salary = salary + increase
year = year + 1
Output:
Murdock County
Teacher Salary Schedule
Year Salary
---- ------
1 37238.00
2 37982.76
3 38742.42
4 39517.26
5 40307.61
6 41113.76
7 41936.04
8 42774.76
9 43630.25
10 44502.86
11 45392.91
12 46300.77
13 47226.79
14 48171.32
15 49134.75
16 50117.45
17 51119.79
18 52142.19
19 53185.03
20 54248.73
21 55333.71
22 56440.38
23 57569.19
24 58720.57
25 59894.99
26 61092.89
27 62314.74
28 63561.04
29 64832.26
30 66128.90

Answer 2

Your while loop calculates the increase for the year, which is one, and then prints that. But you want to simply print year one as is, correct? So, the simple solution is just moving the print setting to the top of the loop. Year one will be calculated correctly, and then it will change the numbers of the salary and increase before restarting the loop. Like this:
while year < 31 :
print("%4d %15.2f" % (year, salary))
increase = salary * RATE / 100
salary = salary + increase
year = year + 1
Take note, that it will calculate the next salary/increase on the last loop, but not print it. Alternatively, add a print line before the loop that prints year one, such that the loop starts on year 2 (full code for second example):
RATE = 2.0
INITIAL_SALARY = 37238.00
salary = INITIAL_SALARY
year = 1
print("Murdock County")
print("Teacher Salary Schedule")
print()
print("Year Salary")
print("---- ------")
#Changed to so that salary does not increase after 20 years.
print("%4d %15.2f" % (year, salary))
while year < 31 :
if year < 20:
increase = salary * RATE / 100
salary = salary + increase
year = year + 1
print("%4d %15.2f" % (year, salary))
else:
year = year + 1
print("%4d %15.2f" % (year, salary))
Gives the output below, note that salary does is increased on year 20. If you do not want this, change the 20 in the if statement, to 19, so that it stops adding the increase one year earlier:
Murdock County
Teacher Salary Schedule
Year Salary
---- ------
1 37238.00
2 37982.76
3 38742.42
4 39517.26
5 40307.61
6 41113.76
7 41936.04
8 42774.76
9 43630.25
10 44502.86
11 45392.91
12 46300.77
13 47226.79
14 48171.32
15 49134.75
16 50117.45
17 51119.79
18 52142.19
19 53185.03
20 54248.73
21 54248.73
22 54248.73
23 54248.73
24 54248.73
25 54248.73
26 54248.73
27 54248.73
28 54248.73
29 54248.73
30 54248.73
31 54248.73