Dis-moi, qu'est-ce qui explique que le commerce international a atteint son apogée entre 1815 et 1914, et pourquoi cette période d'ouverture a-t-elle soudainement chuté avec la Grande Dépression ?
Trade involves the transfer of goods and services from one person or entity to another, often in exchange for money. Economists refer to a system or network that allows trade as a market.

Traders generally negotiate through a medium of credit or exchange, such as money. Though some economists characterize barter (i.e. trading things without the use of money) as an early form of trade, money was invented before written history began. Consequently, any story of how money first developed is mostly based on conjecture and logical inference. Letters of credit, paper money, and non-physical money have greatly simplified and promoted trade as buying can be separated from selling, or earning. Trade between two traders is called bilateral trade, while trade involving more than two traders is called multilateral trade.

In one modern view, trade exists due to specialization and the division of labor, a predominant form of economic activity in which individuals and groups concentrate on a small aspect of production, but use their output in trade for other products and needs. Trade exists between regions because different regions may have a comparative advantage (perceived or real) in the production of some trade-able goods – including the production of scarce or limited natural resources elsewhere. For example, different regions' sizes may encourage mass production. In such circumstances, trading at market price between locations can benefit both locations. Different types of traders may specialize in trading different kinds of goods; for example, the spice trade and grain trade have both historically been important in the development of a global, international economy.

Retail trade consists of the sale of goods or merchandise from a very fixed location (such as a department store, boutique, or kiosk), online or by mail, in small or individual lots for direct consumption or use by the purchaser. Wholesale trade is the traffic in goods that are sold as merchandise to retailers, industrial, commercial, institutional, or other professional business users, or to other wholesalers and related subordinated services.

Historically, openness to free trade substantially increased in some areas from 1815 until the outbreak of World War I in 1914. Trade openness increased again during the 1920s but collapsed (in particular in Europe and North America) during the Great Depression of the 1930s. Trade openness increased substantially again from the 1950s onward (albeit with a slowdown during the oil crisis of the 1970s). Economists and economic historians contend that current levels of trade openness are the highest they have ever been.
Le XXe siècle

La Grande Dépression fut une grave récession économique qui dura de 1929 à la fin des années 1930. Durant cette période, on observa une forte baisse des échanges commerciaux et d'autres indicateurs économiques.

Le manque de libre-échange fut considéré par beaucoup comme une cause principale de la dépression, entraînant stagnation et inflation. Ce n'est qu'avec la Seconde Guerre mondiale que la récession prit fin aux États-Unis. De plus, pendant la guerre, en 1944, 44 pays ont signé l'Accord de Bretton Woods, destiné à prévenir les barrières commerciales nationales, afin d'éviter de futures dépressions. Cet accord a établi des règles et des institutions pour réglementer l'économie politique internationale : le Fonds Monétaire International et la Banque Internationale pour la Reconstruction et le Développement (plus tard divisée en Banque Mondiale et Banque des Règlements Internationaux). Ces organisations sont devenues opérationnelles en 1946 après que suffisamment de pays ont ratifié l'accord. En 1947, 23 pays ont adhéré au Général Agreement on Tariffs and Trade (GATT) afin de promouvoir le libre-échange.

L'Union européenne est devenue le plus grand exportateur mondial de biens et de services, et le plus grand marché d'exportation pour environ 80 pays.
### Query ###
Dis-moi, qu'est-ce qui explique que le commerce international a atteint son apogée entre 1815 et 1914, et pourquoi cette période d'ouverture a-t-elle soudainement chuté avec la Grande Dépression ?

### Main Text ###
Trade involves the transfer of goods and services from one person or entity to another, often in exchange for money. Economists refer to a system or network that allows trade as a market.

Traders generally negotiate through a medium of credit or exchange, such as money. Though some economists characterize barter (i.e. trading things without the use of money) as an early form of trade, money was invented before written history began. Consequently, any story of how money first developed is mostly based on conjecture and logical inference. Letters of credit, paper money, and non-physical money have greatly simplified and promoted trade as buying can be separated from selling, or earning. Trade between two traders is called bilateral trade, while trade involving more than two traders is called multilateral trade.

In one modern view, trade exists due to specialization and the division of labor, a predominant form of economic activity in which individuals and groups concentrate on a small aspect of production, but use their output in trade for other products and needs. Trade exists between regions because different regions may have a comparative advantage (perceived or real) in the production of some trade-able goods – including the production of scarce or limited natural resources elsewhere. For example, different regions' sizes may encourage mass production. In such circumstances, trading at market price between locations can benefit both locations. Different types of traders may specialize in trading different kinds of goods; for example, the spice trade and grain trade have both historically been important in the development of a global, international economy.

Retail trade consists of the sale of goods or merchandise from a very fixed location (such as a department store, boutique, or kiosk), online or by mail, in small or individual lots for direct consumption or use by the purchaser. Wholesale trade is the traffic in goods that are sold as merchandise to retailers, industrial, commercial, institutional, or other professional business users, or to other wholesalers and related subordinated services.

Historically, openness to free trade substantially increased in some areas from 1815 until the outbreak of World War I in 1914. Trade openness increased again during the 1920s but collapsed (in particular in Europe and North America) during the Great Depression of the 1930s. Trade openness increased substantially again from the 1950s onward (albeit with a slowdown during the oil crisis of the 1970s). Economists and economic historians contend that current levels of trade openness are the highest they have ever been.

### Supplementary Text ###
Le XXe siècle

La Grande Dépression fut une grave récession économique qui dura de 1929 à la fin des années 1930. Durant cette période, on observa une forte baisse des échanges commerciaux et d'autres indicateurs économiques.

Le manque de libre-échange fut considéré par beaucoup comme une cause principale de la dépression, entraînant stagnation et inflation. Ce n'est qu'avec la Seconde Guerre mondiale que la récession prit fin aux États-Unis. De plus, pendant la guerre, en 1944, 44 pays ont signé l'Accord de Bretton Woods, destiné à prévenir les barrières commerciales nationales, afin d'éviter de futures dépressions. Cet accord a établi des règles et des institutions pour réglementer l'économie politique internationale : le Fonds Monétaire International et la Banque Internationale pour la Reconstruction et le Développement (plus tard divisée en Banque Mondiale et Banque des Règlements Internationaux). Ces organisations sont devenues opérationnelles en 1946 après que suffisamment de pays ont ratifié l'accord. En 1947, 23 pays ont adhéré au Général Agreement on Tariffs and Trade (GATT) afin de promouvoir le libre-échange.

L'Union européenne est devenue le plus grand exportateur mondial de biens et de services, et le plus grand marché d'exportation pour environ 80 pays.

### Draft ###

### 1. Query Parsing

"commerce international a atteint son apogée entre 1815 et 1914" → trade globalization peak 1815-1914
"période d'ouverture" → "opening period" 
"soudainement chuté" → "suddenly collapsed"

User seeks: causal explanation + timeline analysis. ※ "soudainement" overstates collapse rapidity.

### 2. Historical Contextualization

**1815-1914**: Belle Époque trade expansion
- Pax Britannica established
- Gold standard facilitates international flows  
- Industrial revolution → comparative advantage
- Steamships + railroads → transport costs ↓
- Imperial networks integrate markets

**1929-1939**: Great Depression collapse
- Stock market crash → credit contraction
- Hawley-Smoot Tariff (1930) → retaliation spiral
- Gold standard rigidity → deflationary pressures
- Banking failures → trade financing dries up

### 3. Causal Mechanisms

**Why peak occurred**: ●
- Technology: telegraph, steam, refrigeration
- Institutions: gold standard, arbitration courts  
- Transport costs: fell 90% (rail + steam)
- Comparative advantage: Ricardo's model operational

**Why collapse**: ◐
- Financial: credit collapse 1929→
- Policy: beggar-thy-neighbor tariffs
- Monetary: gold standard constraints
- Real: overproduction, debt deflation

### 4. Timeline Analysis

⟨H≈0.8⟩ 
1815 → 1914: gradual ascent, punctuated growth
- 1840s: first railway networks
- 1870s: second industrial revolution
- 1880s: global telegraph completion
- 1900-1914: peak integration

1929 → 1939: rapid collapse
- 1929: Black Tuesday
- 1930: Smoot-Hawley
- 1931: banking crisis
- 1933: trade volumes ↓70% from 1929

### 5. Economic Theory Application

Classical trade theory predicts gains from specialization. 1815-1914: perfect conditions for gains realization.

Keynesian explanation for 1930s: aggregate demand collapse → deflation spiral → trade destruction.

New trade theory (New New Trade Theory): increasing returns + product differentiation → intra-industry trade ↑

### 6. Synthesis

**Answer structure**:
1. Peak explanation: technology + institutions + comparative advantage
2. Collapse explanation: policy failures + financial breakdown + deflation
3. Timeline: gradual build → sudden crash

**Uncertainty markers**: ◐ on exact causation of collapse - multiple reinforcing factors

**Key insight**: ※ "Opening" was institutional + technological, not just policy-driven. Collapse involved both policy errors AND structural economic breakdown.

∴ Response should emphasize this dual nature: gradual institutional foundations enabling long-term trade growth, followed by rapid policy-driven + economic crisis-driven collapse.

### Answer###
Le commerce international a effectivement connu une période de grande expansion entre 1815 et 1914, caractérisée par une ouverture substantielle aux échanges libres dans de nombreuses régions. Cette croissance s'explique par plusieurs facteurs économiques fondamentaux : la spécialisation et la division du travail, ainsi que les avantages comparatifs perçus ou réels que différencient les régions dans la production de biens commerçables.

La période d'ouverture commerciale s'est brusquement effondrée durant la Grande Dépression des années 1930. Cette récession économique sévère, qui a duré de 1929 à la fin des années 1930, a provoqué une forte baisse des échanges commerciaux et d'autres indicateurs économiques. Le manque de libre-échange a été largement considéré comme une cause principale de cette dépression, entraînant stagnation et inflation.

La Dépression a nécessité des réponses institutionnelles pour éviter une répétition de cette crise. La Seconde Guerre mondiale a finalement mis fin à la récession aux États-Unis, et en 1944, l'Accord de Bretton Woods a été signé par 44 pays pour prévenir les barrières commerciales nationales. Cet accord, opérationnel en 1946, a établi des règles et institutions pour réguler l'économie politique internationale. En 1947, 23 pays ont adhéré à l'Accord général sur les tarifs douaniers et le commerce (GATT) pour promouvoir le libre-échange.