GDX and GDXJ vs. GLD

How are behaviors of physically backed gold and gold miner exchange-traded funds (ETF) similar and different? To investigate we consider SPDR Gold Shares (GLD) versus both Market Vectors Gold Miners (GDX) and VanEck Vectors Junior Gold Miners ETF (GDXJ). Using weekly returns for GDX since May 2006 and GDXJ since November 2009, and contemporaneous weekly returns for GLD and the S&P 500 Index (SP500), all through June 2019, we find that: