The ENR Top 100 Green Design Firms generated $4.50 billion in design revenue in 2011 from projects registered with and actively seeking certification from third-party ratings groups under objective sustainable-design standards. The Top 100 had $589.6 million in revenue from green projects outside the U.S. in 2011, up 33.1% from $442.9 million in 2010. Designers are finding increased interest from owners in sustainable design thanks to the promise of increased efficiency in building operations. Owner-occupied commercial buildings, Class A commercial rental buildings and major urban centers are almost all achieving LEED certification at some level. While many design firms say the recession has had little or no impact on interest in sustainable design, others see some owners backing off a little. There is focus on reducing energy use, reducing water use, commissioning, measurement and verification, and other sustainable practices that have real operational savings and return on investment.