- Turkestan - remote, exotic and of some significance to the Great Game
- Afghanistan - of strategic interest to the British Empire in India
- Bactria - a historical area roughly coincident with Afghanistan and part of Turkestan
- Central Asia - to pick up more generic interest
- Silk Road - again to pick up more generic interests.
Essentially showing that:
- There is a peak of interest in Afghanistan in the 1880's and the 1980's
- Interest in Central Asia climbs and remains roughly constant from some time in the 1850's
- Interest in Turkestan declines from 1950 onwards reflecting much of the regions closed status in the Soviet Union and post 1949 China
- Relatively speaking no one gives a stuff about Bactria or the Silk Road
- The British English corpus shows an interest in Afghanistan developing around 1850 and remaining largely constant with peaks around 1880 and 1980
- Paralelling this an interest in Central Asia developing around 1850 and remaining constant to today
- An interest in Turkestan from the start of the Great Game around 1880 and remaining till around 1950 when the region became closed to foreigners
- A peak of interest in Bactria just after 1950 when the Afghanistan was accessible to foreign archaeologists
- Not a lot of interest in the Silk Road
- American interest in any of the terms was minimal until some time around 1880
- Americans don't, on the whole, give a stuff about Bactria - it's a British thing
- Interest in Afghanistan roughly increases linearly until around 1980, when people suddenly sit up and take notice of what's happening and then falls off after the Soviet withdrawal
- Interest in Central Asia grows steadily paralleling interest in Afghanistan, until around 1980 when it drops off coincident with the peak of interest in Afghanistan
- Interest in Turkestan grew steadily, tracking developing interest in Afghanistan and Central Asia generally, until around 1940 when interest dropped off due to the region becoming closed to foreigners
- The Silk Road doesn't do it for Americans either
- Americans where not particularly interested in Central Asia much before 1880. The British were interested earlier, and given the history of British Imperial expansion in India and the desire to establish a friendly client state in Afghanistan that's perhaps not surprising
- American interest developed increasingly throughout the twentieth century, while British interest remained constant
- The closing of Turkestan to foreigners led to a diminution of interest post 1950. And while I havn't posted the graph, running the query for Xinjiang in preference to Turkestan shows a similar result
- The Soviet conflict in Afghanistan is reflected in an increase of interest, more so on the part of Americans, because of the perceived geopolitical implications.