Intensive crop farming
Intensive crop farming is an agricultural system designed to maximize crop yields per unit of land through high inputs of synthetic fertilizers, pesticides, irrigation, mechanization, and often high-yielding crop varieties, typically on smaller land parcels compared to extensive methods.[1][2]
Pioneered and accelerated by the Green Revolution starting in the 1960s, which disseminated semi-dwarf wheat and rice varieties alongside chemical inputs, this approach dramatically boosted global cereal production, averting widespread famines and supporting population growth from about 3 billion to over 7 billion people.[3][4]
By concentrating production on less land—a strategy known as land sparing—intensive methods have empirically reduced habitat conversion pressures compared to low-yield alternatives, preserving more area for biodiversity.[5]
However, reliance on non-renewable inputs has led to documented drawbacks, including soil nutrient depletion and erosion, eutrophication from fertilizer runoff, pesticide resistance, and declines in agro-biodiversity, prompting debates over long-term sustainability.[6][7][8]
Definition and Principles
Core Definition
Intensive crop farming constitutes a production system aimed at maximizing crop output per unit of land area through the deployment of elevated inputs, including synthetic fertilizers, pesticides, irrigation water, mechanized equipment, and genetically selected high-yielding varieties. This approach prioritizes land efficiency over expansive land use, enabling higher productivity to meet commercial or population-driven demands while minimizing the land footprint relative to output.[9][10] In contrast to extensive farming, which depends on larger land expanses with limited external amendments and results in lower yields per hectare—often 1-2 metric tons for maize in low-input regions—intensive methods routinely achieve 5-10 times greater productivity; for instance, U.S. corn yields average 9.4 metric tons per hectare under intensive conditions.[11][12] Key operational traits include reduced fallow periods, monoculture or rotation schemes optimized for yield, and continuous monitoring via technology to sustain soil fertility and control biotic stresses.[13] These practices stem from economic imperatives to intensify resource application where land is constrained, as evidenced by global adoption in densely populated or high-value arable zones.[14]Fundamental Principles
Intensive crop farming rests on the principle of maximizing output per unit of land by systematically addressing biological and environmental constraints on plant growth through elevated inputs of capital, labor, and materials. This approach recognizes that crop yields are inherently limited by scarcest resources—such as nutrients, water, and protection from pests—per Liebig's law of the minimum, which posits that growth is controlled not by total available factors but by the most deficient essential input.[15] Intensive methods counteract these limits by supplying synthetic fertilizers, irrigation, and agrochemicals to elevate production beyond natural baselines, enabling multiple harvests or higher biomass per cycle.[16] A foundational tenet is the high-input, high-output model, where external amendments directly enhance photosynthetic capacity, root development, and reproductive output; for instance, nitrogen fertilizers alone have accounted for 30–50% of global crop yield gains since the mid-20th century by fulfilling protein synthesis and chlorophyll formation needs.[6] Empirical evidence from the United States demonstrates this causality: average corn yields rose from approximately 1.6 tonnes per hectare in the early 20th century to 9.5 tonnes per hectare by the late 20th, driven by fertilizer adoption alongside hybrid seeds and irrigation, with total factor productivity growth persisting without slowdown through 2011.[11][17] Globally, wheat yields increased 225% from 1961 to recent decades, maize by 196%, and rice by 146%, attributable to intensified input use that overcomes soil nutrient depletion and variable rainfall.[18] This paradigm prioritizes land efficiency over extensification, substituting capital for land to support population growth; however, it assumes diminishing returns unless inputs are optimized, as excess applications can lead to inefficiencies like nutrient runoff without proportional yield uplift.[19] Crop-specific management—such as tailored nutrient balancing—ensures that multiple limiting factors (e.g., phosphorus for energy transfer, potassium for osmosis) are addressed concurrently, rather than sequentially, to achieve synergistic gains.[20] Sustainable intensification within this framework seeks to maintain these principles while mitigating externalities, though core reliance on input escalation remains the causal driver of elevated productivity.[21]Historical Development
Early Foundations
The foundations of intensive crop farming trace back to the Neolithic Revolution, which began approximately 12,000 years ago in the Fertile Crescent region of the Near East, where hunter-gatherer societies transitioned to sedentary agriculture through the domestication of wild plants such as emmer wheat, einkorn wheat, and barley.[22] This shift enabled higher population densities by extracting more calories per unit of land, though initial practices relied heavily on manual labor and rudimentary tools rather than advanced inputs.[23] Early farmers cleared forests and practiced slash-and-burn techniques, but intensification emerged as communities developed permanent fields and selective breeding to improve yields.[24] In Mesopotamia, by around 5000 BCE, Sumerian societies advanced these practices into large-scale intensive cultivation, incorporating mono-cropping of staple grains like barley and wheat alongside organized irrigation systems of canals and levees to manage the Tigris and Euphrates rivers' unpredictable floods.[24] These innovations allowed for surplus production that supported urban centers and specialization, with fields yielding multiple harvests annually under controlled water distribution, marking a departure from extensive foraging toward labor-intensive land management.[25] Soil salinization from over-irrigation posed early challenges, prompting adaptations like fallowing, which foreshadowed later sustainability concerns in intensive systems.[24] Similarly, in ancient Egypt from the Predynastic Period around 6000 BCE, Nile River floods deposited nutrient-rich silt, facilitating basin irrigation where farmers constructed earthen dikes to retain water and cultivate emmer wheat, barley, and flax on predictable floodplains.[26] This system supported two to three crops per year with minimal rainfall dependency, achieving high yields per acre through dense planting and animal-drawn plows by 4000 BCE, which laid groundwork for centralized agricultural economies.[26] Comparable developments occurred in the Indus Valley and Yellow River basins, where riverine irrigation enabled intensive rice and millet farming, underscoring how geographic advantages in alluvial soils drove early intensification across civilizations.[23]Green Revolution Era
The Green Revolution, spanning primarily from the 1940s to the 1980s, represented a pivotal shift toward intensive crop farming through the development and dissemination of high-yielding crop varieties (HYVs) that demanded substantial inputs of fertilizers, pesticides, and irrigation to achieve their potential. Initiated in Mexico under the Rockefeller Foundation's program starting in 1943, agronomist Norman Borlaug bred semi-dwarf wheat varieties resistant to lodging and responsive to nitrogen fertilizers, elevating average wheat yields from approximately 750 kg per hectare in the early 1950s to over 3,200 kg per hectare by the late 1960s.[27] These HYVs formed the core of intensive practices, as traditional varieties could not efficiently convert added nutrients into biomass without structural collapse, necessitating a high-input model to maximize output per unit land.[28] By the mid-1960s, these technologies expanded to Asia, particularly India and the Philippines, via institutions like the International Rice Research Institute (IRRI), which released the IR8 rice variety in 1966—a short-statured cultivar that doubled yields under optimal conditions compared to local strains. In India, wheat production surged from 12 million metric tons in 1965 to 20 million metric tons by 1968 following the importation of Mexican HYV seeds, while rice output similarly increased, enabling double-cropping and averting widespread famine amid population growth.[4] Cereal yields across adopting regions in Asia rose by 30-50% on average within a decade of HYV adoption, driven by this intensification, though gains were uneven and concentrated on irrigated lands suitable for heavy inputs.[27][29] Intensive farming during this era hinged on expanded chemical and water inputs: global fertilizer application escalated from 14 million nutrient tons in 1950 to over 80 million by 1980, with HYV-dependent regions like Punjab, India, seeing nitrogen use rise tenfold to sustain yields exceeding 4 tons per hectare for wheat.[30] Pesticide deployment similarly intensified to combat pests in monocultural HYV fields, while irrigation coverage in India expanded from 17 million hectares in 1951 to 38 million by 1971, often via tube wells drawing groundwater.[3] This package yielded global cereal production tripling since the 1960s, but it entrenched dependency on non-renewable inputs, with overuse leading to soil nutrient imbalances and salinization in some areas.[30][29] The era's legacy in intensive crop farming lies in demonstrating causal links between targeted breeding, input intensification, and yield escalation, enabling food supply to outpace demographic pressures in key regions without proportional land expansion. However, productivity plateaus emerged by the 1980s as diminishing returns to fertilizer application set in, underscoring the finite responsiveness of even optimized HYVs without further innovations.[4][28]Modern Expansions
Following the Green Revolution's focus on high-yielding varieties, synthetic fertilizers, and expanded irrigation primarily in the mid-20th century, intensive crop farming expanded through biotechnology and digital technologies starting in the 1990s.[4] The commercialization of genetically modified (GM) crops marked a pivotal shift, with the first GM tomato approved in 1994, followed by widespread adoption of herbicide-tolerant soybeans, insect-resistant corn, and cotton from 1996 onward.[31] By 2024, GM varieties accounted for over 90% of U.S. corn, cotton, and soybean acreage, enabling higher yields through pest resistance and reduced tillage, which contributed to global GM cropland expanding from 1.7 million hectares in 1996 to 185 million hectares by 2016.[32] [33] Precision agriculture further intensified farming practices by integrating GPS, sensors, and data analytics to optimize inputs at sub-field levels, originating from theoretical work in the 1980s and practical implementation with GPS-guided machinery in the mid-1990s.[34] The first GPS auto-guidance systems appeared in 1996, evolving into variable-rate application of fertilizers and pesticides by the early 2000s, which allowed farmers to target applications based on soil variability and crop needs, reducing waste while maintaining or increasing productivity.[35] These technologies proliferated globally, with adoption accelerating in North America, Europe, and Australia, driven by declining sensor costs and improved satellite accuracy. This era saw substantial global crop production gains, with agricultural output nearly quadrupling from 1961 to 2020, much of the post-1990 increase attributable to intensification rather than land expansion, including doubled cereal yields in many regions through combined GM traits, precision tools, and sustained high inputs.[36] [37] Expansions extended to developing countries, such as Bt cotton adoption in India and China from the late 1990s, boosting yields by 20-30% in some cases while curbing insecticide use, though outcomes varied by local agroecological conditions.[33] Overall, these advancements supported a 53% rise in per capita food availability despite population growth, underscoring intensive methods' role in sustaining output amid finite arable land.[36]Technologies and Practices
Mechanization
Mechanization in intensive crop farming refers to the deployment of powered machinery to perform labor-intensive tasks such as soil preparation, planting, cultivation, and harvesting, enabling large-scale operations with reduced human input. This shift, prominent since the early 20th century, has been foundational to achieving high yields through uniform field management and timely interventions. Tractors, introduced commercially with John Froelich's gasoline-powered model in 1892, supplanted animal traction and facilitated deeper tillage and precise implement control, contributing to a surge in cultivated acreage.[38] By leveraging fossil fuels, tractors amplified labor productivity, with U.S. farm output expanding nearly threefold from 1948 to 2021, in part due to mechanical advancements.[39][40] Central technologies include seed drills, evolved from Jethro Tull's 1701 mechanical version for row planting to minimize seed waste and enable inter-row cultivation, and combine harvesters, which integrate reaping, threshing, and cleaning to process crops like wheat and corn at rates exceeding manual methods by factors of 10 to 20.[41] Modern iterations incorporate GPS-guided auto-steer systems and variable-rate applicators, allowing for site-specific management that optimizes input use in intensive monocultures.[42] In high-input systems, these machines support dense planting densities and multiple cropping cycles annually, as evidenced by mechanized U.S. corn farms achieving average yields of over 170 bushels per acre by 2020, compared to under 50 bushels in non-mechanized historical baselines.[43] The economic rationale stems from labor substitution, where machinery reduces per-unit costs in expansive fields; for instance, combine harvesters cut harvesting labor needs by up to 90% in grain production, fostering scalability essential for intensive farming's yield targets.[44] However, adoption varies globally, with FAO data indicating that only about 10% of crop farmers in regions like sub-Saharan Africa use tractors, limiting intensive practices there, while mechanization levels in developed nations correlate with productivity gains of 1-2% annually from efficiency improvements.[45][46]Chemical and Biological Inputs
Chemical fertilizers, including nitrogen (N), phosphorus (P), and potassium (K) compounds such as urea, ammonium nitrate, superphosphate, and potash, provide precise nutrient supplementation to soils in intensive crop systems, compensating for rapid depletion from high planting densities and repeated harvests.[47] The Haber-Bosch process, scaled industrially from 1913 onward, revolutionized nitrogen availability, enabling the intensification of agriculture by supporting higher crop biomass and yields unattainable with natural soil fertility alone.[48] In the United States, annual application of these fertilizers sustains production of major crops like corn and soybeans, with nitrogen rates often exceeding 100 kg/ha in high-yield regions to match crop demands.[49] Peer-reviewed analyses confirm that synthetic fertilizers underpin yield advantages in conventional intensive systems, where organic alternatives yield 24-50% less per hectare due to slower nutrient release and lower total input efficiency.[50][51] Pesticides—encompassing herbicides, insecticides, and fungicides—control biotic stresses exacerbated by monocultures and dense planting in intensive farming, preventing yield losses from weeds, pests, and pathogens.[52] Herbicides suppress competition from weeds, contributing up to 50% yield gains; fungicides and insecticides add 17% each in treated fields compared to untreated baselines.[53] In the U.S., pesticide active ingredients applied to 21 major crops peaked at 314 million pounds in 1981 before declining to around 200 million pounds by the 2000s, driven by integrated pest management and herbicide-tolerant crops, yet remaining essential for maintaining outputs in fertilizer-intensive rotations.[54] Crop-specific data show pesticides explain substantial variance in application rates, with species like cotton or potatoes requiring higher volumes than diversified systems, underscoring their role in enabling uniform, high-density production.[55] Biological inputs, such as biofertilizers (e.g., nitrogen-fixing bacteria like Rhizobium or phosphate-solubilizing microbes) and biopesticides (e.g., Bacillus thuringiensis toxins or entomopathogenic fungi), introduce living organisms to enhance nutrient cycling or pest suppression without full reliance on synthetics.[56] In intensive contexts, these are integrated as supplements—e.g., microbial inoculants applied with chemical N to boost uptake efficiency by 6-10%—rather than replacements, given scalability limits and variable field efficacy compared to calibrated synthetics.[57][58] Global adoption remains niche, with biopesticides comprising under 5% of total pesticide markets as of 2024, though growth in multi-strain formulations targets resistance management in high-input systems.[59] Empirical trials indicate biologicals improve soil microbial activity but yield less consistently in nutrient-poor or pest-pressured intensive fields without chemical backups.[60]Genetic Engineering and Breeding
Selective breeding has been foundational to intensive crop farming since the mid-20th century, involving cross-pollination of plants with desirable traits such as higher yields and disease resistance to develop hybrid varieties that maximize output on limited land.[61] This method relies on natural genetic variation within species, often requiring multiple generations of selection, and contributed significantly to yield doublings in staples like maize and wheat during the Green Revolution.[62] In intensive systems, hybrids enable denser planting and monoculture practices, though they necessitate annual seed purchases due to loss of hybrid vigor in offspring.[63] Genetic engineering, introduced commercially in 1996 with crops like herbicide-tolerant soybeans and Bt cotton, differs by inserting specific genes—often from unrelated organisms—into a plant's genome using techniques like Agrobacterium-mediated transformation or gene guns.[33] This precision allows targeted traits such as insect resistance via Bacillus thuringiensis (Bt) toxin genes, reducing crop losses by 13-20% in adopting regions, and herbicide tolerance enabling no-till farming that preserves soil structure.[64] By 2024, over 90% of U.S. corn, soybeans, and cotton acreage featured genetically engineered (GE) varieties, reflecting farmer adoption driven by net economic gains estimated at $34.3 billion globally from 2010-2012 through yield boosts and input savings.[65] [33] Empirical data indicate GE crops have enhanced intensive farming productivity, with meta-analyses showing average yield increases of 22% worldwide while cutting insecticide use by 37% in Bt crops.[33] For instance, Bt maize in the U.S. averted losses equivalent to 5-10% of potential yields annually from pests like the European corn borer.[64] However, National Academies reviews note that GE adoption has not accelerated overall yield growth trends beyond conventional breeding but has stabilized outputs by mitigating biotic stresses.[66] Recent advances like CRISPR-Cas9 genome editing, operational since 2012, enable precise modifications without foreign DNA insertion, accelerating trait development in crops such as rice and wheat for improved root architecture and yield components.[67] Studies report 17-23% yield gains in edited wheat and enhanced stress tolerance in tomatoes, supporting intensive systems' demands for resilient, high-output varieties amid climate variability.[68] [69] Regulatory frameworks in major producers treat many CRISPR edits akin to conventional breeding, facilitating faster deployment.[67]Irrigation and Soil Management
Irrigation constitutes a cornerstone of intensive crop farming, enabling cultivation of high-yield crops in arid and semi-arid regions where rainfall is insufficient, thereby supporting multiple harvests per year and stabilizing production against climatic variability.[70] In the United States, irrigated farms accounted for a disproportionate share of output value despite comprising only 18% of cropland in 2022, with irrigation mitigating yield losses from precipitation deficits and temperature extremes.[70] [71] Globally, converting rainfed to irrigated cropland could boost production by approximately 20%, though this demands precise water application to avoid inefficiencies.[72] Common methods include surface (furrow or flood), sprinkler, and drip systems, with the latter two offering higher efficiency—typically 80-95% for drip versus 50-70% for surface—by minimizing evaporation and runoff.[73] [74] Subsurface drip irrigation further enhances efficiency by delivering water directly to roots below the soil surface, reducing weed growth and surface evaporation while supporting intensive schedules for crops like maize, where yields in drylands have increased by 55% relative to rainfed systems.[75] [76] Sprinkler systems excel in salt leaching, crucial for sustaining soil productivity in saline-prone areas, whereas furrow methods suit row crops but risk uneven distribution without gated pipes for improved uniformity.[73] [77] Soil management in intensive farming focuses on countering degradation from repeated cultivation, including erosion, compaction, and nutrient depletion, which arise from tillage exposing soil to wind and water forces while monocropping exhausts specific minerals.[78] [79] Conservation practices such as reduced or no-till farming preserve soil structure by leaving crop residues on fields, cutting erosion rates by up to 90% compared to conventional tillage and fostering microbial activity that rebuilds organic matter.[80] Integrated nutrient management—combining synthetic fertilizers with organic amendments and crop rotations—maintains soil fertility, preventing declines observed in over-cropped systems where vegetables have lost up to 30-50% of key micronutrients since the mid-20th century due to extraction exceeding replenishment.[80] [81] Irrigation exacerbates salinization risks in intensively farmed soils, where poor drainage and over-application concentrate salts, affecting 33% of global irrigated lands and reducing yields for salt-sensitive crops at levels exceeding 4 dS/m electrical conductivity.[82] [83] Mitigation involves leaching fractions during off-seasons and selecting salt-tolerant varieties, alongside monitoring to avert irreversible degradation in regions like California's Central Valley, where salinization has impaired productivity on thousands of hectares.[84] These strategies sustain long-term viability, as unchecked salinization can halve crop outputs in affected fields.[85]Productivity and Economic Outcomes
Yield Enhancements
Intensive crop farming achieves yield enhancements primarily through synergistic applications of high-yielding varieties (HYVs), synthetic fertilizers, irrigation, and pest management, enabling outputs far exceeding those of low-input systems. These methods have driven global cereal yields from an average of about 1.2 metric tons per hectare in 1961 to over 4 tons per hectare by 2020, with intensification accounting for roughly two-thirds of production growth in developing regions.[86] The causal mechanism involves optimizing biophysical limits: HYVs partition more biomass to harvestable organs under controlled nutrient and water availability, while inputs mitigate abiotic and biotic stresses that constrain photosynthesis and resource capture.[87] The Green Revolution exemplified early yield gains, with semi-dwarf wheat and rice varieties—developed in the 1960s—boosting annual yield growth by up to 1.3 percentage points in adopting areas, particularly for these staples. In developing countries, wheat and rice yields increased by an average of 208% per hectare from pre-1960 baselines to the 1990s, as these varieties resisted lodging under high fertilizer doses and supported denser planting. Empirical data from Mexico, where yields tripled for wheat between 1943 and 1963 following HYV introduction, underscore the role of genetic improvements coupled with irrigation expansion. Fertilizers amplified these effects; nitrogen applications alone contribute 40-50% to final yields in fertilized systems by enhancing photosynthetic capacity and tillering.[88][89][21] Irrigation further elevates productivity by stabilizing water supply, with irrigated lands yielding 2-3 times more than rainfed equivalents for crops like maize and rice. In China's drylands, irrigation raised maize yields by 55% through reduced evapotranspiration stress and sustained growth periods. Globally, expanding irrigation to current rainfed cropland could increase production by 20%, though actual gains depend on soil and climate interactions.[76][72] Genetic engineering has extended these enhancements in modern intensive systems, with GM crops delivering an average 22% yield advantage over non-GM counterparts across traits like insect resistance and herbicide tolerance. From 1996 to 2013, GM adoption correlated with over 370 million additional metric tons in global food crop output, driven by reduced yield losses from pests and weeds. Peer-reviewed meta-analyses confirm these gains hold across regions, though marginal returns vary with baseline management intensity.[90][33][33]| Factor | Yield Impact Example | Source |
|---|---|---|
| HYVs (Green Revolution) | +208% for wheat/rice in developing countries (pre-1960 to 1990s) | [88] |
| Fertilizers | 7.5 kg grain per kg nutrient; N: 40-50% of yield | [21][91] |
| Irrigation | +55% for maize in drylands; potential +20% global | [76][72] |
| Genetic Engineering | +22% average for GM crops | [90] |
Contributions to Food Security
Intensive crop farming has substantially bolstered global food security by elevating crop yields and total production, thereby enhancing food availability amid population expansion. Since 1961, global cereal yields have tripled, enabling cereal production to outpace a doubling of world population over the same period without proportional increases in cultivated land.[27] This intensification, reliant on mechanization, fertilizers, improved seeds, and irrigation, has spared an estimated land area equivalent to the combined sizes of the United States and India from conversion to agriculture, preserving ecosystems while sustaining output growth.[27] The Green Revolution, a pivotal phase of intensive farming from the 1960s onward, exemplifies these gains through high-yielding varieties and input packages, which increased wheat yields by 208%, rice by 109%, and maize by 157% in developing countries between 1960 and 2000.[4] These advancements raised food supply per capita by 12–13% in developing regions from 1960 to 1990, averting a projected 11–13% decline in caloric availability and preventing hunger for millions.[4] Consequently, the prevalence of undernourishment in developing countries fell from 33% in 1970 to 12% by 2015, reflecting the causal link between yield surges and reduced chronic hunger.[92] Beyond immediate output, intensive practices have supported poverty alleviation tied to agricultural productivity; for instance, each 1% increase in crop output correlates with a 0.48% poverty reduction in Asia.[4] In regions like South Asia, these methods averted large-scale famines projected in the mid-20th century, stabilizing food systems and enabling socioeconomic development.[4] While challenges like uneven adoption persist—evident in Sub-Saharan Africa's lagging yields—the empirical record underscores intensive farming's role in scaling production to feed over 8 billion people as of 2023, with global primary crop output reaching 9.9 billion tonnes.[93]Economic and Trade Effects
Intensive crop farming has driven substantial economic growth by amplifying agricultural output per unit of land and labor, enabling surplus production that supports domestic food affordability and international trade balances. In the United States, where intensive practices such as mechanized planting, chemical fertilizers, and hybrid seeds predominate, the agriculture, food, and related industries sector contributed $1.537 trillion to gross domestic product in 2023, equivalent to 5.5% of total GDP, with productivity gains from these methods accounting for the majority of output expansion since the mid-20th century.[94][95] Similarly, in developing regions adopting intensive techniques post-Green Revolution, such as parts of Asia, yield doublings in staple crops like rice and wheat correlated with GDP per capita increases of 20-30% in affected countries between 1960 and 1990, as higher farm incomes spurred rural investment and urbanization.[96] On trade fronts, intensive farming's yield enhancements have fostered comparative advantages in commodity exports for nations with advanced infrastructure, skewing global agricultural trade toward high-productivity exporters like the US, Brazil, and Argentina. U.S. agricultural exports reached $175.5 billion in 2023, primarily in intensively produced grains and oilseeds, generating multiplier effects that added $362.4 billion to the broader economy through downstream industries like processing and transportation.[97][98] Empirical analyses indicate that expansions in high-yield agriculture have increased virtual water and calorie trade flows, with net exporter countries experiencing trade volume growth of up to 50% per decade from 1961 to 2010, while reducing global food price volatility by enabling buffer stocks.[99] However, this dynamic has also intensified import dependency in low-yield regions, where subsidized exports from intensive producers depress local prices and hinder smallholder competitiveness, as evidenced by net import surges in sub-Saharan Africa correlating with a 15-20% decline in domestic farm revenues post-2000.[100]| Key Economic Indicators (U.S., 2023) | Value |
|---|---|
| Agriculture's GDP Share | 5.5% ($1.537 trillion)[94] |
| Export Value | $175.5 billion[97] |
| Total Economic Contribution from Exports | $362.4 billion[97] |