A weak or strong currency can lead to a shift in index value, so it pays to be aware of Forex rates.
So for example, 2014 saw the value of the USD soar against the JPY. Valued at 1:102 early in the year, by the end of the year it had moved to 1:120. In this period the Nikkei 225 grew by a significant margin, going from around a 14-15k level to nearly 18k.
So how exactly can the fortunes of a nation’s currency affect its major index? In this example, a weakened JPY was positive news for Japan’s exporters, the biggest of which play a key role in the country’s economy. The more fragile Yen allowed exporters to sell their products abroad for a lower price than, whilst still retaining a similar profit margin in their own currency. With export-focused companies invigorated, revenue and profits were could be boosted, which in turn meant that stock levels rose and consequently drove up the Nikkei.