• People sometimes view membership in social groups as being zero-sum: belonging to one social group excludes you from being a member of a different group.
• People sometimes view gender hierarchies in the workplace as being zero-sum, which can cause them to be more opposed to gender-fair policies.
• People sometimes believe that there is an inherent zero-sum competition between different ethnic groups, which can cause them to develop negative attitudes towards immigrants.
• People sometimes view racism as a zero-sum game, meaning that they believe that a decrease in racism against one group will be balanced by an increase in racism toward other groups.

• Mistaken belief in limited resources: assumeing that a certain resource is more limited than is actually the case.
• Mistaken belief in trade-off consistency: assuming that there must be a tradeoff between the various advantages and disadvantages of each option, so that the options must be balanced overall.
• Common correlations: certain types of tradeoffs or problems tend to be frequently correlated with each other, which can cause people to assume that they exist even in situations where they don’t.
• Previous experience: people mistakenly assume that a certain situation is zero-sum because they were exposed to similar situations in the past that were in fact zero-sum. 

To reduce the degree to which you experience the zero-sum bias, you need to identify cases where you assume that a certain situation is zero-sum, and then assess the situation rationally in order to identify whether it is actually zero-sum, which you can do, for example, by asking yourself whether a resource under consideration is truly limited.