Just downloaded historical data from dukascopy, but when I plotted Volume against time, I think there are a few irregularities and problems in the data. I donwloaded 5 minute bar data of BID prices from 01.01.2013 to 31.03.2017 for EURUSD pair. I have attached the plot of Volume data of BID bars below.
For example, there is a a huge cluster of spikes in volume around the beginning of July 2014 and another cluster around September 2016. Apart from these clusters the volume data seems consistent from the start of 2013 to the end of March in 2017.
Are these spike clusters based on some fat-tail event or just irregularities with the data?