100 Yen a Day for 10 Years - How Much Do You Accumulate?
Dropping 100 yen (about $0.70) into a piggy bank every day is as simple as saving gets. After one year you have 36,500 yen, after five years 182,500 yen, and after ten years 365,000 yen (about $2,500). Enough for a trip or a modest appliance.
But that 365,000 yen has not "grown" - it has merely "accumulated." You have placed 3,650 coins into a box, and the first coin is still worth exactly 100 yen, just like the last one. A piggy bank has no compound interest magic.
The Same 100 Yen in an Index Fund
If you invested 100 yen per day (roughly 3,000 yen per month) in an index fund returning 5% annually, after 10 years you would have approximately 466,000 yen. That is about 100,000 yen more than the piggy bank's 365,000 yen. The extra 100,000 yen was earned by your money "working" for you while you did nothing.
A 100,000 yen gap might seem modest. But extend the timeline and the gap explodes. After 20 years: piggy bank 730,000 yen vs index fund approximately 1,230,000 yen (a 500,000 yen gap). After 30 years: piggy bank 1,095,000 yen vs index fund approximately 2,500,000 yen (a 1,400,000 yen gap). Even with just 100 yen a day, 30 years of compound interest creates a 1.4 million yen difference.
The Piggy Bank Has Its Merits Too
The numbers clearly favor the index fund, but piggy banks have genuine advantages. First, they are ideal for building the habit of saving. For children or anyone who has never saved regularly, the physical act of dropping a coin into a box each day trains the "saving muscle."
Second, there is zero risk of losing principal. Index funds can decline in the short term - your 100 yen might temporarily become 90 yen. A piggy bank's 100 yen stays 100 yen forever (inflation erodes its real value, but the nominal amount never drops). Third, instant access. Selling an index fund takes a few days; opening a piggy bank takes a second.A stylish piggy bank on your desk can boost your motivation to save.
The Best Approach: Piggy Bank + Index Fund
It does not have to be one or the other. Use both. Keep "money you might need soon" in a piggy bank, and put "money you won't touch for 10+ years" into an index fund. For example, drop 100 yen a day into a piggy bank and invest 3,000 yen a month into a NISA (Japan's tax-advantaged investment account) index fund. When the piggy bank reaches 100,000 yen, deposit it at the bank and move half into your index fund. The key is building a system for saving. The piggy bank creates the habit; the index fund harnesses the power of compound interest. This two-pronged approach is the most realistic way to grow your wealth without strain.