According to Deutsch, states may form a security community if the current state of the international system increases "unattractiveness and improbability of war among the political units concerned". For instance, security concerns led the United States and Mexico to form a pluralistic security community in anticipation of World War II. Deutsch identified two conditions that should facilitate formation of a pluralistic security community. The first one is "the capacity of the participating political units or governments to respond to each other's needs, messages, and actions quickly, adequately, and without resort to violence". One way states build this capacity is by common membership in international organizations. The second condition is the "compatibility of major values relevant to political decision-making". An example of a major politically relevant value given by Deutsch is political ideology. However, more recent empirical research showed that the often hypothesized role of liberal values and general trust in the development of security communities is overestimated. Another test, by Michael Haas, compared successful with unsuccessful security-community-oriented organizations, finding that the principal variable with a statistically significant relationship out of Deutsch's 12 variables was mutual compatibility of main values.