Unusually relaxed and undemonstrative for a business leader, Ben Noteboom insists that he’s not obsessed with work. But the chairman and CEO of staffing giant Randstad Holding keeps charging ahead in a fiercely competitive industry.

Since Noteboom took over in 2003, Randstad has nearly tripled its annual revenue, to €14.2 billion ($19.7 billion) last year. It’s now the world’s second-biggest human resources provider after Switzerland-based Adecco. Much of this expansion has come from mergers and acquisitions, especially the 2008 takeover of Dutch rival Vedior — then the No. 4 player globally — in a €3.3 billion deal.

But Noteboom, 53, also excels at driving organic growth, almost single-handedly at times. In 1997 he set up Randstad Inhouse Services from scratch to provide on-site human resources services. At first, sitting in an eerily quiet office with only a secretary reporting to him, Noteboom wondered if he’d made a big mistake. But the unit delivered more than €2 billion in revenue last year.

To offset economic cycles in what is often a low-margin business, Amsterdam-based Randstad’s broadly successful strategy has been to push up volumes. During the first six months of 2011, revenue jumped 17 percent over the same period last year, to €7.6 billion. The earnings before interest, taxes, depreciation and amortization margin was only 3.4 percent, compared with 3 percent in the first half of 2010.

Founded in 1960 by Ger Daleboudt and Frits Goldschmeding — the latter is still its top shareholder, with a 30 percent stake — Randstad has some 27,500 employees and roughly 4,200 offices. Temporary staffing across most sectors, about 40 percent of it blue-collar, makes up the bulk of its business; on any given day it deploys half a million workers under the brands Randstad, Rowlands International and Tempo-Team. But fees for permanent placements yield an outsize share of profits: 10 percent, compared with less than 2 percent of revenue.