JAKARTA: Economic growth in Indonesia should cause the number of middle class and affluent consumers to nearly double by 2020, a study has predicted.

The Boston Consulting Group estimated that the amount of Indonesians fitting into this demographic would surge from 74m in 2012 to 141m by 2020, as the country's GDP continues to expand.

Similarly, the number of cities and regencies housing 500,000 members of this cohort is set to jump from 25 to 54, which has "huge implications for the way businesses operate," according to the report.

Greater Jakarta will contain 30m such consumers by the end of the decade, versus 18m in 2012. These totals hit 47m and 24m respectively for the rest of Java, with Sumatra's figures doubling to 34m.

"The typical middle class Indonesian rides a motorbike and shops at a mix of local stores," the analysis added. "Very few have the luxury of air conditioners or a car."

Indeed, fully 91% of this audience regularly buy household supplies from warungs – or small, family–run shops – at present, as do 80% from minimarts. Roughly half also visit wet markets.

"These traditional retail formats have constraints that make them less than ideal. Consumers cited product assortment and availability as key barriers for warungs and a chaotic atmosphere as the principal deterrent for wet markets," the study said.

Over the longer term, however, there is likely to be a shift from "convenience to comfort", as smartphones enhance their current middle class penetration from 22%. Penetration currently stands at 29% for PCs.

The increasing maturation of the financial services sector should assist this process, with approximately three-quarters of the Indonesian middle class already possessing a bank account.

Higher up the income spectrum, some 52% of affluent shoppers own a washing machine, and a majority drive a car. Credit cards, furthermore, are witnessing a rapid improvement in uptake.

As almost all households in Indonesia have a TV set, this remains the "most important" source of product information, alongside word of mouth and advice from sales people and marketing messages.

There were also over 50m users of Facebook, the social network, in Indonesia last year, and 29m members of Twitter, the microblog, with more tweets originating in Jakarta than any other city worldwide. Rising mobile web use should boost these platforms.

Data sourced from Boston Consulting Group; additional content by Warc staff