Final answer:
Catron includes the statistic to support her argument that same-sex marriage legalization is essential for legal rights and benefits.
Step-by-step explanation:
The statistic that "61 percent of cohabitating same-sex couples were married" is included in Catron's paragraph to support her argument that same-sex marriage legalization is essential for legal rights and benefits. By highlighting the high percentage of cohabitating same-sex couples who choose to get married, Catron is emphasizing that marriage is a significant goal for these couples, indicating the importance and relevance of same-sex marriage. This statistic provides evidence that legalizing same-sex marriage is crucial for ensuring equal rights and protections for these couples.