Structural unemployment is due to changes is various sectors of the economy. These continuous changing conditions in different industries are due to changes in tastes of consumers and are part of any changing society. While structural unemployment can be reduced by retraining, for most part it is desirable since it is a reflection of a society seeking improvements in its products.
In the mid 1980's the decrease in the price of oil caused many oil related undertakings (in particular in Texas) not to be profitable any more. Some oil drilling and explorations were cut and the employees let go. Such employees would be considered as part of the structural unemployment of the country.