For some it is the direction of house prices, for others it is length of hemlines.
For those trying to see through the current global economic fog and work out how bad things may get, enlightenment can come in many forms.
Sales of scotch whisky are regarded by some as a fair, if unusual, barometer of economic prospects and how confident people feel about the present and the future.
"I tend to believe there is a correlation between the two," says Paul Hughes, director of the International Centre for Brewing and Distilling at Heriot Watt University.
The reason for this is fairly simple.
Global reach
Scotch is a truly global product sold in more than 200 countries.
Though it may not be a staple item or a commodity, like oil, which is traded by the second and whose price is tracked in minute detail, it is enjoyed in most corners of the world and therefore a decent indicator of broader buying patterns.
Historically, scotch sales have tended to follow the global economic curve.
In the last 30 years, the value of sales has only fallen three times: in 1983, 1998 and 2004.
So what does the industry's performance last year tell us about the current state of things?
At face value, things don't look too bad at all.
Following recent trends, 2007 was another storming year with sales, both in terms of export volumes and their total value, eclipsing previous records.
More than 1.13 billion bottles were shipped overseas, 8% ahead of the previous year.
These sales created income of £2.2bn, itself a 15% increase on 2006.
Equally encouraging was the geographical spread of growth.
Of the top ten markets by value, only two suffered a drop in income with Spain, Greece, Germany and South Africa all showing exceptional growth.
In volume terms, only two countries retreated.
A luxury too far?
However, significantly, one of the these was the US where volumes slid 5%.
The US has always been the industry's most important market, with sales worth £100m more than any other country.
The value of US transactions continued to rise last year - up 5% - but does the fall in volumes signal much tougher times around the corner this year?
BIGGEST SCOTCH MARKETS: 2007
Scotch is widely marketed as an "affordable luxury", but will the housing crisis and the credit crunch blighting the US inevitably make it a luxury too far for many more people or simply unaffordable?
Distillers feel the US market has so far remained resilient despite the clear economic strain and are closely watching developments to see if the picture worsens.
But recent precedents for a severe economic downturn on the industry's fortunes do not make for happy reading.
The Asian financial crisis of the late 1990s sent markets such as South Korea and Taiwan into a tailspin and the industry took four or five years to fully recover.
Experts think the impact of the current US downturn could be less dramatic unless the fallout spreads to other markets.
"The impact will be more muted," Paul Hughes argues. "The proportion of disposable income that a bottle of whisky costs in the US is far less than in Asia."
Emerging markets
The industry feels much better prepared for a slowdown that at any time in the last 30 years, having made real inroads in potent, emerging markets where Scotch was once seen as a curiosity.
Of these, its progress in China, South Africa and Russia - in itself a microcosm of global economic trends - has been the most exciting.
Scotch has become a lifestyle drink for the growing number of wealthy young professionals living in Chinese cities such as Beijing, Shanghai and Guangzhou.
The industry has lobbied hard for specific trademark protection in China, conscious that the premium nature of the product means it is particularly prey to counterfeiters.
Direct sales to China actually fell last year, but the industry says this is misleading because more shipments are passing through other regional ports, particularly Singapore.
The South African market has almost doubled in the last five years, mirroring the country's own economic development, and it now accounts for 70% of all sales to Africa.
Of the growth markets, Russia remains the most enigmatic.
A country with no real whisky-drinking heritage, growth there has helped by the boom in tourism to the UK, which has led many Russians to visit Scotland.
EU enlargement has also opened up much of Eastern Europe, with sales to Poland boosted by the abolition of tariffs.
'Not complacent'
While it may be nervous about the US, as long as emerging markets remain strong and strides are made in unlikely countries such as Colombia, which bought £17m in scotch last year, the industry is likely to remain in pretty good shape.
"We are certainly not complacent about future prospects and we are looking at market movements very carefully to see how things are developing, not just in the US," explains David Williamson, from the Scotch Whisky Association.
"But we are seeing broad-based growth in the industry. With exports to 200 markets that does mitigate any regional fluctuations."
Whisky accounts for 12% of all Scottish exports and a quarter of UK food and drink exports.
Given this, the industry's cautiously upbeat tone will reassure many about the future although maybe not all economists.
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