A person saving $12.40 a week from age 20 to age 65 at 7% would have over $200,000 when they retire. However, no one working full time makes only $100/wk. At minimum wage, 12.4% of income would yield $600,000 at retirement. But it would really be a stretch to imagine a person earning minimum wage their entire working life, much less the ridiculous $100 scenario of yours.
Math is your friend.
@Hoodat I know math is my friend. I don't think it is yours,though. There were damn few women earning 100 bucks a week in the 50's and 60's when that woman was working. My father was a 1st class framing and trim carpenter,and I was sent to the store every Friday night to cash his check for him,and the biggest paycheck he ever received in his entire working life was right at 130 bucks for a weeks work with overtime. Granted,housing and other living expenses were MUCH lower back then,but I doubt the typical woman worker brought home 75 bucks a week.
In other words,there is no way in HELL they are going to save an additional 12 bucks a week for 20 or 30 years. Most likely she would do something like put it in a Christmas Club savings account so she would have the "extra" money to buy presents for her family at Christmas.
The ONLY people who save money on a regular basis are the people who take home more than they need to spend,week in and week out. For example,if my father had been bringing home 200 a week at the time when a typical working-class family could get by fairly comfortably on 100 bucks a week,there is no doubt he would have saved money. Remember,he grew up scrambling to get the money to feed himself and his younger brothers and sisters every week,so he knew what kind of desperation being broke brings.
In FACT,he did manage to save money. Being a working young adult during the Depression and remembering the closed banks with missing deposits,he didn't trust banks,but he did manage to hide money in the house that he would use to buy a new car every 5 or 6 years as he needed one. He always paid cash because having payments scared the hell out of him.
Not a chance in hell he was ever going to pull 12 bucks a week out of his paycheck to save for a future he might never live to see,though.
And he did live long enough to start drawing Social Security checks when he turned 62 and it was too hard for him to keep a job anymore. Without forced "Savings" through SS,he would have been screwed in his old age.