I don't know if there are any studies of what it would mean to the *world* economy, but with respect to the US, Robert Fogel wrote a famous article which I once cited in soc.history.what-if
https://groups.google.com/d/msg/soc.history.what-if/TxHuWjWI1mA/ptGDJGhW52gJ as a legitimate thought experiment, despite its lack of a plausible POD:
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"Thought experiments" where there is no plausible POD have a legitimate
place. They are particularly common in economic history. For example,
Robert Fogel famously argued in *Railroads and American Economic Growth*
(1964) that building no railroads at all would have had only a slight
effect on the US gross domestic product before 1890. See
http://groups.google.com/group/soc.history.what-if/msg/04442e974be80a36
for some of his arguments.
Now there is no plausible POD for there being no railroads built in
nineteenth century America. (Horrendous accidents on the early railroads
bring a ban on construction? Hardly likely, since there *were* plenty of
horrendous accidents on the early railroads, and people accepted them as
the price of Progress. Canal interests bribe legislators to ban
railroads? There were just too many legislators in too many states to
bribe, and anyway there would be public outrage at banning a technological
advance that other advanced nations were embracing.) Yet Fogel's inquiry
seems to me both perfectly legitimate and significant--since statements
like "Railroads contributed enormously to American economic growth in the
nineteenth century" had been commonplace, and one cannot properly evaluate
such statements without considering how the American economy would have
grown without railroads. (Whether Fogel reached a correct conclusion is
of course another matter.)