Are there any buggy whip makers left in your family? Times change and people get retrained for other jobs.
There are going to be jobs in the gas and oil business in the USA for some time to come, but your position makes no logical sense. Are these people ONLY capable of building oil tanks? Is there any other use for their skills?
When I started out as a law clerk, word processors didn't exist. I used an IBM Selectric, scissors, clear tape, and a photocopier, to draft and edit contracts and docutments. We searched title by pouring over large metal bound books at the Land Registry Office, and I spent a lot of time going back and forth to government offices to search various records. Today, everything is done online. I can search title from the comfort of my own home, using my laptop. Closings are completed without going to the Registry Office. An entire generation of highly paid title searchers and conveyancers were put of out work.
For years, people in the areas of the country which grew tobacco, resisted any restrictions on the sale of cigarettes because it was a "personal choice", and a lot of jobs would be lost in the tobacco industry. The tobacco lobby was enormous. Now smoking is considered odious at best, and tobacco farmers turned to other crops.
Back in the early 90's, there was a book called "Green is Gold" which spent a good number of weeks on the NYT Best Seller List, and was a wake up call to business all across North America. Instead of seeing the green movement as a threat, view it as an opportunity. Patrick Carson, the author, was a Loblaws Grocery Vice President, and the company wholeheartedly embraced this philosphy, and became the leading grocer in Canada.
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Are you saying your relatives can't find another market for their tanks? What did buggy makers do?