Accenture Ltd. is going Indian.

The Bermuda-based consulting firm last week said it would supplement the 27,000 workers it already has in India by hiring an additional 8,000 people there by August 31.

India will soon be Accenture’s biggest employee base worldwide, overtaking the US.

The motivation behind the move is quite plain to see.

Even after several years of 15 percent pay increases, an experienced software developer in Bangalore costs about $13,000 a year, compared with $78,000 in Atlanta, according to the PayScale.com web site.

The economics is compelling, and not just for Accenture.

International Business Machines Corp. has announced plans to triple Indian investments to $6 billion by 2009.

Hiring people cheaply is going to be only half the battle.

India’s home-grown software-services companies, which have benefited the most from arbitraging on the wage differential, won’t give in to their deeper-pocketed rivals, such as Accenture and IBM, without a fight.

Indian companies have a pricing constraint because they don’t have the consulting expertise of big-bulge firms. Nevertheless, they have controls that allow for a very profitable use of their human resources.

What makes Indian software-services companies a hit with shareholders is that they are run with efficiency.

Take Tata Consultancy Services Ltd.

The Mumbai-based company is the biggest Indian exporter of technology services.

Unlike in the past when it did low-end work such as application support and development, Tata Consultancy is now competing with Accenture and IBM for more-lucrative “outsourcing” projects where the in-house software team of a large company has to be taken over and managed.

Revenue productivity — or sales per employee — is growing 1.25 percent a year. That’s the icing on the cake: Most profits are still coming from efficient management of the company’s explosive growth.

S. Padmanabhan, the human-resource chief at Tata Consultancy, looks at three numbers every evening: People hired that day; workers who left; and the “utilisation ratio,” or the proportion of billable employees that day to the total.

With 83,500 employees currently on board and 125 people joining every day, it isn’t easy for a company like Tata Consultancy to keep a tight rein on the utilization ratio.

It is nonetheless critically important for it to do so.

If utilisation dips more than half a percentage point from 78 percent, the revenue for the quarter may miss the target; investors may be disappointed; the stock may fall. The number rising too much above 78 percent isn’t good, either.

The system needs some slack to allow people to train in new technologies and to move from one project or location to another.

If this “fluidity” is missing, as Padmanabhan explained to me in an interview in Singapore last week, it shows that hiring should have been more brisk a month earlier. More employees would have led to higher revenue and greater profit.

With as much as 51 percent of the revenue spent as wages, there is no substitute for efficient management of human resources. It holds the key to sustaining the level of profitability that investors have come to expect from Indian software companies.

Tata Consultancy’s pre-tax income was about 27 percent of sales in the most recent quarter, compared with a margin of 11 percent at Accenture and less than 15 percent at IBM, according to data compiled by Bloomberg.

Since its shares began trading in August 2004, Tata Consultancy has given investors an annualised 54 percent return in US dollar terms. That’s three times the money that shareholders have made from investing in Accenture. In this period, IBM returned less than 8 percent a year.

The biggest risk Indian software companies are facing right now at home is attrition rates as high as 18 percent.

As Accenture and IBM step up hiring, retaining workers will become an even bigger challenge.

Keeping workers in by throwing more money at them hurts profitability. The long-term solution lies in giving employees more training when they are fresh graduates, followed by overseas stints, “from Alaska to Wellington,” as Padmanabhan puts it.

When people are tired of globetrotting, they must be given new roles. Help in finding a job for the spouse, a good school for the children and a nice apartment for a family come next.

The attrition rate at Tata Consultancy is less than 11 percent, the lowest among the top five Indian software companies. Women’s participation in the workforce is 25 percent, up from 17 percent in 2004.

It’s not clear if IBM and Accenture will be able to — or even want to — replicate the Indian model in its entirety even as they boost their presence in the country to cut costs.

For a start, adopting the flexibility of companies nurtured on outsourcing will be hard for those that have built their reputations on proprietary technology or a deep understanding of the client’s business. The market, however, may force the change.

Thanks to the Indian companies, investors have come to appreciate that the real money in the so-called knowledge businesses lies in a combination of explosive growth and efficient utilisation of human resources. And that’s more than just hiring cheap labour.

Andy Mukherjee is a Bloomberg News columnist. The opinions expressed are his own.