The percentage is 0%. "Lead" in this case is a misnomer. Pencil "Lead" is made of graphite (an allotrope of carbon) and different levels of clay to control hardness.
When the graphite deposit that produced the first pencils was discovered, the people thought it was lead. Later, chemists told them it was graphite, a form of carbon, but the 'lead pencil' had...
Pencils have never contained the metal, lead, although the word commonly used to describe the centre core of a pencil is, in English, 'lead'. The ancient tool which preceded the modern pencil was a...