BLK chart, page-200

They've improved through put and efficiency which is positive but the truth is the pits are a bowl ,heavily tapered ones so gold being heaviest settles at the bottom , meaning high AISC to start overburden, mud , landslips and rocks but as you get through the middle to lower pay getting better each layer down with less obstacles then pay and rock from bed rock at the bottom if they go that far , then back fill .