％。
Imported cars account for less than 8%.
Literal
Imported-cars [topic-は] 8% under [only-しか] not-occupying.
占める (しめる, 'to occupy, account for') is the standard verb for market share statistics. しか~ない emphasizes the smallness — 'only less than 8%.' 未満 (みまん, 'less than') is a precise technical term, distinct from the approximating 以下.