Indeed percentages can be very confusing.
- When people talk about a 20% drop in price it means that the new price is 20% lower than the old one e.g a 1000K property drops to 800K (1000 x 0.8 = 800). Similarly a 20% rise means 1000 x 1.2 = 1200.
- But when people talk about a property being 20% overvalued, it means that the current price is 1.2 times the "real value", thus the real value of a 1000K property is 833K (1000 / 1,2 = 833).
- So paradoxically if a 20% overvalued property drops by 20% it hasn't reached its real value at all. New price is 800K while real value is 833K. It's now undervalued by 4% (800 / 833 = 0.96).
- That 20% overvalued property needs to drop by 17% to reach its real value (1000 x 0.833 = 833).
- Now say a property drops by 20% then rises back by 20%, one would think it has gone back to its original price... not! (1000 x 0.8 x 1.2 = 960). Similarly a property that has risen by 20% then dropped 20% would be worth 1000 x 1.2 x 0.8 = 960, the same!
- A property that drops 10% then another 10% has actually dropped only 19% (1000 x 0.9 x 0.9 = 810)
Now going back to properties being overvalued by 80%. A 1000K property's real value would be 555K (1000 / 1.8 = 555). i.e. almost half. If it drops to that level then the yield would be almost double. An investor stampede would ensue that would lift prices again, but to come back to its original price it needs to rise by... 80%. No trap this time, I got you! (555 x 1.8 = 1000)
Edit: Sorry, Boeman, you beat me by several minutes.