original: Progress in developing the TAR was hindered by political and economic obstacles throughout the 1960s, 1970s and early 1980s.
simplifications: TAR development was slowed by political and economic barriers in the 1960s, 1970s and early 1980s. Developing the TAR was challenged by political and economic obstacles from the 1960's - early 1980's. Political and economic obstacles slowed the development of the TAR during the 1960s, 1970s and early 1980s. Progress in making the TAR was hurt by political and economic difficulties through the 1960s, 1970s and early 1980s. Progress developing the TAR was prevented by political and economic obstacles throughout the 1960s, 1970s and early 1980s. Political and economic problems prevented the TAR from being developed in the 1960s to early 1980s. Progress in developing the TAR was hindered by political and economic obstacles during the 1960s, 1970s and early 1980s TAR's development was slowed down by political and economic obstacles from the 60s to early 80s. The advance in making the TAR was slowed by political and economic issues from the 1960's through the early 1980's. The political and economic barriers throughout the 1960s, 1970s and early 1980s  delayed the development of the TAR.