The scatterplot above shows the number of visitors to a railroad museum in Pennsylvania each year from 1968 to 1980, where represents the number of years since 1968 and represents the number of visitors. The x-axis shows the years since 1968, and the y-axis shows the number of annual visitors. A line of best fit is also shown. In the context of this scatterplot, what does the -intercept of the line of best fit signify?
The total number of visitors over the entire period.
The average number of visitors per year.
The estimated number of visitors in the first year of data collection (1968).
The rate at which the number of visitors increased each year.
