Ramie  posted some info this morning on the performance drag between $NUGT and $GDX during 2015.  Here’s a recent example.

2/12 GDX closed at $18.84  $NUGT closed at $56.87

2/18 GDX closed at $18.90  $NUGT closed at $54.72

So in just a few days, GDX returned to basically the exact same level but NUGT was more than $2 lower.