The phrase "a key index of" is correct and usable in written English.
It can be used to indicate an important measure or indicator of a particular quality or condition.
Example: "The unemployment rate is often considered a key index of the overall health of the economy."
Alternatives: "a crucial indicator of" or "a significant measure of".
At Southwest, the time it takes to get a plane that has just landed ready for takeoff — a key index of productivity — is, on average, twenty minutes, and requires a ground crew of four, and two people at the gate.
The mess may be the nail in the coffin for Mr Aso, who was already labouring under a 9.7% approval rating.And a key index of manufacturing activity in New York plummeted in February.
A key index of emerging market stocks has fallen by 10% since its May peak.
U.S. Industry Battered In October The Sept. 11 attacks exacted a swift and painful toll on the nation's factories, driving a key index of U.S. manufacturing activity to lows that mirror the 1990-1991 recession.
And since consumption, alongside income, occupation and education, is a key index of middle-class membership, it is not surprising that popular media and cultural representations of the middle class are mostly associated with their consumption and lifestyles (Guo 2008; Rocco 2017).
A key index of home builder confidence fell last month, an industry trade group said.
The concept of kinetic energy decay ratio is introduced as a key index to evaluate the effectiveness of a damper design in suppressing cable vibration.
In addition, we examined the relationship between the amount of oxygen sorption and calculated the Goldschmidt's tolerance factor which is a key index to characterize the stability of perovskite structure.
The estimated LOD and LOQ should serve as a key index to characterize fundamental performance of the oligonucleotide microarray system using the two common fluorescence dyes.
Solar fraction ratio is a key index and reference of solar hot water system design, andis also a key factor to evaluate solar hot water system according to Evaluation Standard for Application of Renewable Energy in Buildings in China.
Understand that the key index of a recession is the sustained decline in the real gross national product of a period of time, that is, the total market value of finished goods and services - adjusted for inflation.
