As everyone knows and your chart shows, the gap between ABX and gold pricing has widened significantly especially over the past 2 years.  Most senior gold miners had a similar experience.  For ABX the main reasons are well known;

1   internal decision making such as buying Equinox

2  internal execution including huge capital costs and delays in Pueblo Viejo and Pascua Lama

3  in general costs have been rising faster than expected (similar story at competitors)

4  All gold companies have seen their multiples drop ( P/E,  cash flow,  etc)

Will this trend continue?  I think not, at least not for very long.  P/E is now approximately 8 at current gold prices.  This implies a 12.5% in invested money which is 4 or 5 times the interest rates.  The 2015 P/E is about 6 based on current gold and silver prices.

My forecast.  The trend is about to end.  Overshooting happens all the time in the stock market and this is a great example.