In 2007, The Pew Research Center did a follow up survey to one done in 1990 regarding what makes a marriage work and here is what they found:
In 1990 95% of those surveyed said that faithfulness was the most important ingredient in making a marriage work. In 2007 that dropped slightly with 93% indicating faithfulness. Hum….
(Source: http://www.pewsocialtrends.org/pubs/542/modern-marriage)