Deciding how much money goes into a holding, which usually matters more to your result than deciding which holding it is. A stock that triples changes little if it was 2% of your portfolio; one that halves is severe if it was 40%. The practical form is a ceiling on any single position, and a smaller ceiling for the ones you are least sure about. PSEye shows each position's weight and scores how evenly your money is spread.
See every term in the full PSE investing glossary.