Set out how the international parity conditions link to one another

The parity conditions interlock. Covered parity ties the forward premium to the interest differential; if uncovered parity also holds, the expected spot change equals that differential too, so the forward rate is an unbiased forecast: forward rate parity. Ex ante relative PPP links the expected spot change to the expected inflation differential. Fisher splits each nominal rate into a real rate plus expected inflation, so equal real rates across countries give the international Fisher effect. Ex ante PPP plus the international Fisher effect implies uncovered parity. When all hold, the forward premium, expected spot change, interest differential and inflation differential coincide. The trap is thinking covered parity alone makes the forward rate unbiased.