The phrase "accurate barometer" means something that is reliable and trustworthy in measuring or indicating changes or fluctuations in a certain situation or condition. Full definition
Publisher's Weekly is a much more accurate barometer of actual sales. (earlyword.com)
Body composition is a more accurate barometer of overall fitness than scale weight. (coreperformance.com)
MrsBriggs When I heard this, I thought of Mahatma Gandhi's words, and that a more accurate barometer for measuring a country's progress should include the additional indicator of how it treats its homeless companion animals. (baacs.org)