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I was surprised to read these 1938 figures (admittedly estimates) of 1938 GDP for the major combatants of World War II.

In round figures, the U.S. had $85 billion, the Germans $42 billion, Britain $28 billion, Italy $9 billion and Japan $6 billion. Japan's GDP is about 7% of the U.S., 14% of Germany's, less than a quarter of Britain's, and less than Italy's.

Yet, most people would agree that Japan was a larger factor in the war than Italy, because the Allies obtained Italy's surrender in September, 1943, and Japan's two years later. And many would agree that Japan's contribution to the war "approximated" (was half or more) of Britain's, and was a decidedly larger fraction of Germany's (one third to one half) than 14%.

For instance, the Japanese army was larger than the British army (and beat equal or larger numbers of Britishers in battles all over Southeast Asia). If you include British "colonial" forces, e.g. Indians and Africans, and Japan's "colonies" in China and Southeast Asia, the numbers of "British" and Japanese population and troops were about the same. The Japanese navy was about the size of the British navy (and actually stronger because of a larger number of modern ships).

Is it reasonable to assume that my linked figures tell the true story, that Japan did the above with "only" one quarter of Britain's GDP? Are there other relative GDP figures that are more reflective of Japan's relative contribution to the war? Or is it more likely that the linked GDP figures for "Japan only" understate Japan's true war potential because the "Japanese Empire" was a lot larger than just Japan? (At its peak, it included half of China, Indochina, Indonesia and the Philippines (basically today's ASEAN countries), Korea, Taiwan and other Pacific countries.)

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    What do you call as "contribution to war"? If it is a measure of materiel produced, when you compare Japan vs USA it should be noted that 100 of USAAF heavy bombers (B-17/24/29) would not represent the equivalent of 100 Japanes Zeroes / Kates naval airplanes. Even in a fighter vs fighter comparation you would find USA/UK fighters usually having more complex construction (v.g., self-sealing tanks) than Japan models. Additionally, for most of the war Japan was fighting in a secondary scenario (in 1942, against nations unprepared for war or already commited to the war in Europe). – SJuan76 Jun 21 '15 at 22:38
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    Again, (only with the intention of making the question clearer), what would be the formula for "contribution to the war"? Territory controlled? Length of resistence (here Japan would outpeform Germany)? Materiel built? Enemy casualties? Own casualties? – SJuan76 Jun 21 '15 at 22:46
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    Wikipedia gives really different GDP estimates here. The figures are adjusted for inflation, so only ratios matter. Still, Wiki estimates that Japan had a 1/4 the GDP of the US, larger GDP than Italy, 2/3rds the GDP of Germany, etc. Japan's contribution is much more in proportion according to these figures. – two sheds Jun 22 '15 at 2:39
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    @twosheds: Kudos to you for finding an alternate, correct source of figures. – Tom Au Jun 22 '15 at 13:59
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    This question is NOT economically accuarate. The quated figures do not appear to be adjusted for PPP (Purchasing Power Parity) and rather are simply converted into USD using an unkown (although hopefully internally consistant) method. When you look at GDP figures, PPP is a critical factor in understanding the true relative strength of economices in terms of their own production. – Stuart Allan Jun 22 '15 at 16:15
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According to a different set of GDP estimates (which are PPP-adjusted to facilitate cross-national comparisons), Japan's economy is roughly in proportion to @TomAu's estimates of Japan's martial contributions.

For example Tom estimates that Japan contributed more to the war effort than Italy. In every year of the war, Wikipedia estimates that Japan had a larger GDP than Italy. Tom estimates that Japan's contribution was roughly half of Germany's. According to Wikipedia, Japan's GDP was a little under half of Germany's throughout the war. The relative contributions of the Axis powers therefore seem to be fairly proportionate to economic power.

Admittedly, Japan had a much smaller economy than the UK or US. Japan's economy was about a 1/5 of the American economy--but war needs consumed only a 1/3 of American industrial output while Japan devoted nearly all of its heavy industry to military needs. Divide American GDP by 3 and the number is still larger than Japan's GDP, but by much less. Similarly, the UK's enormous GDP is inflated by the colonies, but these were never going to provide heavy industry comparable to the homeland. Looking at just Britain, the UK's GDP is 50% larger than Japan's. Again, assuming that Japan devoted a larger percentage of its industrial resources to military production than did the UK, then their military contributions are roughly proportionate to their economies.

In this sense, Japan was similar to the USSR, another power that (militarily) punched above its (economic) weight. But it's no secret how the USSR did this: Stalin used the powers of the state to turn the Soviet economy toward a complete focus on military production, uprooting entire industries and hundreds of thousands of workers to Siberia. Germany didn't even devote its entire industrial output to military production until 1943.

In short: Among the Axis powers, Japan's military contribution was roughly proportionate to its economy. The fact that it "outperformed" its economy relative to the Allied powers (other than the USSR) is in part due to the fact that the Japanese government devoted a higher proportion of its economic resources to military production than did the US or UK.

  • I would say that Japan outperformed even the figures that you linked. But only to an extent that can be explained by "overachieving." The other interpretation, while extant, isn't plausible. – Tom Au Jun 22 '15 at 15:35
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    @TomAu: Yeah, I agree my answer doesn't explain 100% of the discrepancy. It does make the discrepancy much smaller though, so that strategy/tactics/economic and industrial policy become plausible explanations. – two sheds Jun 22 '15 at 15:40
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    The reason for the discrepancy is that the bulk of Japan's projectable power was prepaid capital accumulated before the war - their Navy, Carrier Air Arm and Pilots. Those resource were unrelated to GDP, and once expended in combat were not replacable by any GDP expenditure. When those were lost in the 42-43 campaigns, the length of the war was only dependent on how long the US would take to recapture the islands Japan had taken, and Japan's GDP was not relevant since they could no longer move produced items to the field, due to the loss of transport. – Oldcat Jun 22 '15 at 21:00
  • @Oldcat: Very interesting comment that would make a good answer. Why don't you vote to reopen (if you haven't already done so) and post this as an answer. – Tom Au Jun 23 '15 at 23:01
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    Canada had a pre-war population of 11,267,000, and fielded 1,029510 effectives in the Royal Canadian Navy, Army, and Air Force combined. This was 9% of the total population and 41% of the male population 18 to 45 years of age (2,474,000). That's a contribution in excess of GDP. Link: canadaatwar.ca/content-7/world-war-ii/facts-and-information – Pieter Geerkens Jun 27 '15 at 4:53

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