Statistics has it that in the years 2000- 2007 GDP in Poland per capita has risen from 10.6 $ to 15.9 $! It mean that purchasing power of average Pole has dropped, about 38%.

I think you've made and error in your calculations. I'm not sure I will be able to explain clearly what I mean but let give it a shoot:

**1. If we compare your calculations:**GDP $ USD/PLN GDP PLN

2000: 10,6 4,3126 45,7 zł

2007: 15,9 2,4754 39,4 zł

with official data:

2000: 19,4 zł

2007: 30,9 zł

then we can clearly see that those two don't match

**2. Why?**I believe the reason is that you've used GDP PPP numbers not nominal GDP with real exchange rates. Because of that when you multiplied GDP PPP by those exchange rates you've did something similar to multipling apples with oranges. This PPP statistics is based on something called "theory of one price" and among other things

**values are not converted with current exchange rate but with some artificial exchange rate** wich would best describe purchasing power of given currency.

I think the way you should do it would be to use nominal values, for example (nominal data from IMF):

2000: 4,45 $ and 19,36 zł

2007: 11,16 $ and 30,87 zł

If you apply your exchange rates to those

**nominal** values of $ above then you will get more or less above values of zlotys.

Ok, mistery solved, what did I win ? ;)

Hm.. if those above is not clear enough, I would like to add something:

When they (IMF, WB, whatever...) are calculating GDP PPP they usually using $ as a common denominator. That is why nominal values of GDP are usually equal with GDP PPP values for United States. Everything is valued against dollar (but probably we could find some Eurostat data, where common denominator is Euro). Anyway what "they" do is they are choosing some arbitral basket of goods and compare purchasing power of currency, ie. how many loaf of bread one can buy with 100 zł. Based on that, they calculate what exchange rate should be in order to buy the same amount of bread in US. In the end

**this artificial exchange rate is used to calculate GDP PPP**. So in the end, the variable here is not GDP in zlotys but the exchange rate which was used to make 10,6 $ from 19,4 zł. To present common way of presenting exchange rates lets revert that question, and we get:

[Artficial Exchange Rate] = 19,4 /10,6 = 1,83.

So the answer is that in order to get Polish GDP PPP in $ in 2000 "they" used 1,8301 artificial exchange rate not 4,3126. Which also means that in year 2000 Polish Zloty was hugely undervalued.