The phrase "a key index" is correct and usable in written English.
It can be used when referring to an important measure or indicator that provides significant information about a particular subject or area.
Example: "The unemployment rate is often considered a key index of economic health."
Alternatives: "a crucial metric" or "an essential indicator."
A key index measuring growth in the service economy dropped in July for the second month in a row to its lowest level since January, the report showed.
The call rate, which is the interest paid when one financial institution borrows money from another, is a key index for short-term interest rates.
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.
Over in the States, a key index measuring sub-prime risks fell to a new low, while investors were awaiting an expected update from Bear Stearns on its exposure to the problem.
The effort has failed to stanch a wave of foreclosures and a decline in home prices, which have fallen for six consecutive months and are now just barely above their recession low, according to a key index updated on Tuesday.
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.
The Labor Department reported Wednesday morning that the Consumer Price Index, a key indicator of inflation, rose by 0.4% in February over the prior month.
St. John's has beaten No. 13 Syracuse and No. 22 Connecticut the last two games to boost its Rating Percentage Index -- a key indicator for the selection committee -- to 17th in the nation.
The index is a key indicator for home sales expected to be completed over the first few months of 2010.
China's official Purchasing Managers' Index (PMI), a key indicator of activity in the sector, stood at 50.6 in December.
Indexes fell more than 2percentt across Asia in early trading Friday, and the Morgan Stanley Capital International Asia Pacific index, a key regional index, was down 2.9percentt by midmorning in Tokyo.
