system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is the EUR falling for the past 6 months? Why is the USD getting stronger?

The EUR/USD went from 1.355 in June 8 2014 to 1.200 January 3 2015.

Last time this happened, it was in 2010, when the EUR went from 1.4  (December 2009) to 1.19 (May 2010).
gpt
The European Central Bank (ECB) are (or rather have already have been) cutting interest rates to try and boost inflation. This hasn't really worked, so they are printing money. The President of the ECB has just in the last few days confirmed that very soon (probably in January) they will enter into full-blown quantitative easing (QE) in the same manner as the Bank of England, the Fed and the Bank of Japan have done. This increases the amount of money in circulation which in theory will hopefully increase inflation. Increasing the amount of money in circulation weakens that currency.

Conversely, the U.S. Has been experiencing a faster than expected rebound to economic health and cutting back their QE programme, ending it completely in November. Improving US data, especially in wages, employment and GDP has meant that the likelihood is now that they will have to raise rates this year, which increases the attractiveness of the currency as it pays a higher yield. 

The result of the above is a falling EURUSD rate. 

Also worth noting that the US dollar is what is known as a safe haven currency. It is seen as a safe place to keep your money, so in times of global turmoil (Ukraine, Israel, Greece, Russia, even Ebola to a certain extent) funds follow a flight to safety and the US dollar gains from simple supply and demand economics. Other safe havens include the CHF and JPY.

<edit>Safe haven stuff.