I believe that brokers’ spreads change because they are affected by market liquidity at any given time. It’s worth noting that spreads can become wider during certain periods – such as just before markets close on Fridays, during major news events, and during holiday seasons (there is lower liquidity when market activity is low). The broker I trade with has really low spreads...I’d say some of the lowest in the industry, so that makes a big difference during normal trading periods. In general, look for a broker with low spreads and then be mindful of popular trading hours and news events (consult an economic calendar).