All the new-builds we design are based on an average seat width of 21". In practice, the widths actually vary from 19" to 22" to achieve staggered seating, if required. The variable seat widths also allow the armrests along the aisle to line up, which looks really good. We typically don't use varied seat width and staggered seating in stadiums, as the sight lines are very good, but we do stagger seats in sloping floor theatres. Most of the larger chains don't use curved rows or variable riser heights, because it's too expensive. Most of our current work is in Latin America and South-east Asia, where labour is cheap and prefabrication is very expensive. Check out our web site at
www.mesbursmith.com to see how great a full stadium auditorium looks with curved rows and variable riser heights.