Zambezi and Zoravia are two developing countries with similar populations. The governments of these countries had adopted a similar health care plan about ten years ago and spend about the same dollar amounts on annual health care. When the health care plan was first​ adopted, the life expectancy of the people of both these countries was approximately 50 years.​ However, after ten​ years, Zambezi showed a much higher average life expectancy compared to Zoravia. What, had it happened during this​ period, would help explain this​ outcome?