Evaluate the tax efficiency of three different holding company structures (e.g., a single-tiered holding company, a two-tiered holding company, and a hybrid structure) for a hypothetical technology company with subsidiaries in the US and EU.  Consider the implications of international tax laws, including transfer pricing regulations and the impact of different corporate tax rates in the US and EU.  Analyze the potential tax benefits and drawbacks of each structure, including the impact on dividend distribution, interest payments, and capital gains.  The analysis should include a detailed comparison of the effective tax rates under each structure and identify any potential risks associated with each.  Your evaluation should be presented in a structured format including a table comparing the three structures across key tax-related metrics, along with a concise summary of the findings and recommendations for the most tax-efficient structure. Assume the technology company generates $50 million in annual revenue, with 60% originating from the US and 40% from the EU.  The company is considering reinvesting a significant portion of its profits for future growth.  Output should include a clear explanation of the methodology used for the evaluation.