Zhèngcè de jiāndìngxìng gěi shìchǎng dàilái le xìnxīn.
The firmness of the policy gave the market confidence.
Tips
grammar
Adjective 坚定 (firm) + nominalizing suffix 性 (-xìng) -> 'the quality of being firm'. The same pattern produces 灵活性 (flexibility), 重要性 (importance), 可能性 (possibility) - useful template for talking about abstract qualities.
register
Formal / written. In speech, 坚定 itself usually does the job: 他很坚定 ('he is very firm'). Reach for 坚定性 in essays, editorials, and policy talk.
