Click the link in the title to see the data and graph.
OPS+ is On Base Percentage Plus Slugging Average adjusted for park and year.
We tend to think that outfielders don't hit much anymore. The data assembled for seasons ten years apart (like the census) derived from baseball-reference.com suggests that 2010 was not too different from the norm for 1940-2010.
The seasons 1910, 1920, 1930 were dominated by Cobb, Ruth, Ruth; the median is in line with other seasons but the low is very low and the difference between the high and low is huge.
2010 shows outfielders bunched more toward the middle.