Answer: Native American population declined dramatically in a period of 50 years.
Explanation: When analyzing a bar graph look for specific data, start by reading the labels provided. The labels on the X and Y axis provide you with information. In this case the graph is very clear: On the left the Y axis label says "Population (in millions)" so it indicates the number of Native Americans alive. On the bottom, the label of the X axis says "Year", that means the numbers 1492 and 1542 are years and the year difference between them is 50 years, therefore the graph indicates that Native American population declined dramatically (from approximately 18 million to about 1 million) in a period of 50 years.
