What does sterling sliding show to us?

Sterling fell to the seven-year lowest point on Monday. The direct cause to the pound depreciation is London major publicly supported Britain leaving the EU. Most of people did not think the election would lead Britain to leave the EU. The depreciation of the pound shows people view an increase in the possibility of Britain leaving the EU and people generally believe leaving the EU has negative effects on Britain. From this case, we can clearly see that the value of currency is still controlled by the market expectation. Usually we see that the central banks and some governments have controls of their currencies' exchange rates. However, their influences on exchange rates are there because the market believe their acts have effects on their economies and based on the effects made to their economies the market will value their countries' currencies. To conclude, governments can only control the market prices by changing the market expectations.