Final answer:
The provided information does not specify the exact percentage of healthcare costs covered by Medicaid in 2017, but indicates substantial spending on various demographic groups.
Step-by-step explanation:
In the calendar year 2017, the specific percentage of health care costs covered by Medicaid in the United States is not directly stated in the provided information. However, we can infer from the available data that Medicaid plays a significant role in healthcare spending. For instance, we know that there was substantial spending on seniors and the blind and disabled, which together accounted for about 64% of Medicaid expenditures, based on figures from (b) showing Medicaid spending. Children represented the largest percentage of enrollment at 47% and received 21% of Medicaid spending. Since Medicaid covers a substantial portion of the market, it is safe to assume that the overall percentage of healthcare costs it covers would be significant, but accurate determination would require specific data from that year.