Definition
Share of voice is a brand's portion of all brand mentions across a fixed set of answers. It only holds if every brand the answers named is counted the same way, including brands that were never on your competitor list.
Why it matters
Asymmetric counting is the most common way this metric lies. If your brand is matched generously and competitors only when they appear on a fixed list, your share is inflated by construction and the report will look encouraging while nothing has improved.
How to measure it
Extract every brand named in each answer, normalise spelling variants to one entity, then divide. Report the total number of distinct brands alongside the share: being 1% of 117 brands is a different situation from 1% of 5.