'Brand voltage' - a handy term coined by WPP-owned market researcher Millward Brown - is a measure used to quantify a brand's success in converting customer awareness into bonding and loyalty.

It is the sum of five indicators: admiration for a brand, affinity to a brand, perceptions of brand innovation, popularity and price.

Judged by these criteria, it seems that dominant UK supermarket chain Tesco, which in 2005 reportedly creamed one pound in every eight spent in the British retail sector, is fast losing its electromotive force.

According to latest BrandZ study from the Warwick-headquartered research agency, the attitude of consumers to Tesco is "you are big and powerful and we don't necessarily like you". The researcher's global brand director Peter Walshe believes Tesco is experiencing "the first signs of the downside of dominance".

"The whole issue of about being dominant and taking over corner shops and being a one-stop-shop is slowly getting into people's conscience," he says. "[Tesco has] got to be confident and humble at the same time if it can possibly do that."

On the BrandZ scale a 'voltage' rating of 3.0 is considered 'strong' and benchmark for future performance. Tesco's voltage has fallen sharply from 5.7 in 2003 to just 1.9 at the end of 2005.

Over the same period, the remaining big four supermarkets rated on the MB brand voltmeter are ...

  • Waitrose: 4.2 (up from 3.4)

  • Sainsbury's: 2.7 (up from 0)

  • Asda/Wal-Mart: 0.7 (down from 3.4).
In real life market share, however, the rankings are reversed. Warns Walshe: "If the quality of that brand is in decline, it's easier for people to slip off and bond with someone else."

Data sourced from MediaGuardian.co.uk and Millward Brown; additional content by WARC staff