Don't waste your time wondering. At the top of nearly every survey about what singles want in a partner is a person who is faithful, loyal, and trustworthy. In other words, singles in a committed relationship want someone who will not cheat on them. Unfortunately, the reality of that desire often comes to a painful end as time goes on. Accurate statistics are hard to come by (because lots of people don’t want to admit to cheating ), but researchers agree that 30 to 50 percent of men and 20 to 40 percent of women are unfaithful . Can you ever know for sure that your partner won’t cheat? No, because people and circumstances change over time. But you can look for specific personal qualities that offer a strong predisposition for faithfulness instead of unfaithfulness. Here's how to know if a guy won't cheat on you.