For branded searches, 20%+ is normal. For non-brand local service searches, 4–8% is solid, under 2% suggests your ad isn't speaking the searcher's language, and double digits usually means tight message match on high-intent terms.
CTR is a diagnostic, not a goal: a high CTR on the wrong searches just spends money faster. Read it per ad group next to the search-terms report. The pair tells you whether the right people are clicking.
The honest caveat on all CTR benchmarks: they swing by industry, match type, and position. Your own trend line beats any published average. A CTR that's climbing while conversions hold is an ad getting better.