Simplest possible(?), but still readable program that shows how a small percentage increase always leads to doubling.

growth.py

"""An extremely simple program that shows how a comparately small
percentage of growth turns into a consecutive doubling of the starting
value.

The strength of the relation between energy and
"""

import time

year = 1
money = 1
original_money = 1
growth = 7

while growth > 1:

    while True:
        print(
            "After year {} of {} % growth we have a nominal sum of {} 'currency'."
            .format(year, growth, money))
        money = round(money + (growth / 100), 2)
        year = year + 1
        time.sleep(0.5)  # ..so that it doesn't print faster than you can see.

        if money >= original_money * 2:
            print()
            print()
            print(
                "At {} % growth the nominal size of the economy doubled after "
                "{} year(s)".format(growth, year))
            print(
                "-------------------------------------------------------------------------------"
            )
            print()
            print()

            money = 1
            growth = growth - 1
            year = 1
            break