What do you mean by “competitive”? Shipping coal adds very little to its cost, so the economic calculation is hardly different for countries that have it and countries that don’t. Perhaps national governments view domestic industries very differently than economists, but you haven’t said how to take this into account. I think Japan explicitly invoked “self-sufficiency” in its decision, perhaps meaning concerns about wartime.
What do you mean by “competitive”? Shipping coal adds very little to its cost, so the economic calculation is hardly different for countries that have it and countries that don’t. Perhaps national governments view domestic industries very differently than economists, but you haven’t said how to take this into account. I think Japan explicitly invoked “self-sufficiency” in its decision, perhaps meaning concerns about wartime.