What is the rule that affects beneficiaries living in someone else's household who do not pay their share of household expenses?

The One Third Reduction Rule is the correct answer because it specifically addresses how the Social Security Administration (SSA) adjusts benefits for individuals who are living in someone else's household and do not contribute to household expenses. Under this rule, when a beneficiary lives with another person and does not pay their fair share of the expenses, the SSA reduces their Supplemental Security Income (SSI) benefits by one-third. This reduction accounts for the understanding that the beneficiary has access to living accommodations that would otherwise incur costs.

Other rules, such as the Exclusion Rule, do not directly pertain to the situation where a beneficiary lives with another individual without contributing financially. The SSI Benefit Adjustment Rule and the Living Arrangement Evaluation Rule are also broader concepts that do not specifically denote the one-third benefit reduction applicable in this context. The One Third Reduction Rule is crucial for understanding the implications of living arrangements on SSI benefits and how income and resource contributions are evaluated.