ZEELAND, MI - Herman Miller Inc. (NASDAQ: MLHR) said fourth quarter North American sales rose more than 40 percent.

For the period ended May 28, 2011, the business furnishings manufacturer said overall net sales reached $441.5 million; an increase of 37.3% from the year ago quarter. Orders reached  $448.5 million, 23% above the 2010 period. 

For the full fiscal year, the furniture maker saw net sales of  $1.65 billion,  a year-over-year increase of 25%. 

"We finished the fiscal year in strong fashion behind continued strength in customer demand and improved operating leverage," said Brian Walker, CEO. "Net sales in the quarter marked our fourth consecutive period of double-digit percentage growth and capped the largest full-year sales increase in our company's history."

Operating expenses in the fourth quarter totaled $114.1 million, an increase of approximately $23 million  after excluding adjustments related to Nemschoff purchase price contingencies and bad debt charges associated with the write-off of dealer receivables in Australia. Higher variable costs associated with increased sales between periods and a return to full employee benefit levels drove the majority of the year-over-year increase in operating expenses, Herman Miller said.