BHP told the market this month that its copper output slipped, and that it will mine less next year. Copper output for the year to June came in below the year before, and the company guided to a further fall in the year ahead. The reason output is falling is the reason he is bullish. The company now expects to dig between 1.65 and 1.8 million tonnes of copper next year, down from about 1.95 million tonnes. For Aitken, that makes BHP, his favourite stock and one of the world’s biggest copper miners, a way to own the shortage.