We gave some economic estimates suggesting that by adopting range voting, countries could expect long-term improvement in their annual economic growth rates of 1-10% additively, which, considering compounding, would ultimately lead to massive advantages.
An entirely different (if crude) way to reach a similar conclusion is to check our historical table of "wrong way elections." Suppose out of 56 US presidential elections, 7 (i.e. one-eighth) have been "wrong way." That rough estimate for the percentage of wrong-way election under plurality voting is supported by the table. (There are also probably even-larger bad indirect effects caused by plurality voting such as numerous good candidates who do not even run due to two-party domination, but we shall not even attempt to estimate those losses here.)
So, with a good voting system, total "forward progress" in 8 elections would be: "8 forward steps." With the poor plurality voting system, we instead get "7 forward and 1 backward step, for net forward progress 6 steps." So countries with good voting systems can expect to "move forward" politically 33% faster.
Of course, even a "perfect" voting system which always gave the voters "what they wanted" would not necessarily deliver the best results, since the voters have been known to guess wrong. (For example, US President Warren G. Harding was elected in 1920 by one of the largest-ever "landslides" but is one of the top choices among historians as "worst US president ever.") My personal estimate is the voters themselves make (what in hindsight was) the wrong choice for about 25% of US presidents – you can make your own guess. If so, a more realistic estimate would be that with good voting systems we make 6 steps forward and 2 back (equals 4 forward) each 8 elections, while with the plurality system it is 5 steps forwards and 3 back (equals 2 forward), in which case countries with good voting systems can expect to "move forward" politically twice as quickly.
Try to translate that into economic improvement in your favorite manner. It is not exactly clear what you'll get, but it is clear it is pretty substantial. (Imagine living for a twice-as-long life. Think you'd accomplish more?)