摘 要
这篇文章是一篇关于经济增⻓类型的学术文章，主要介绍了斯密型增⻓、熊彼特型增⻓、⻢尔萨斯型增⻓和凯恩斯型增⻓四种经济增⻓模式。以下是对这些核心内容的简要概述：
● 斯密型增⻓：
基于各行各业的⽐较优势和专业化分⼯，伴随资本投⼊扩⼤和市场规模延伸。
增⻓表现为国⺠经济产出总量和⼈均产量同时增⻓，是⽔平延拓型增⻓。
受分⼯精细到极致、资本投⼊溢出和极端市场条件限制，终极规模受限。
● 熊彼特型增⻓：
通过企业家精神，借助“创造性破坏”推动生产要素配置创新和技术进步。
增⻓表现为经济集约化和可持续增⻓，兼具⽔平延拓和垂直增⾼特性。
增⻓规模在⻓期视野内没有终极性限制，但仍伴随经济周期波动。
● ⻢尔萨斯型增⻓：
经济产出总量增⻓但⼈均产量下降，原因在于⼈⼝增⻓速度超过产出增⻓速度。
“⻢尔萨斯陷阱”现象，即为⼈均⽣或⽔平在温饱线上下波动。
吴乐旻提出生存品和效用品双部门模型，解释族群生存竞争中的资源分配。
● 凯恩斯型增⻓：
基于消费倾向、资本资产未来收益预期和现⾦流动偏好三个基本⼼理因素。
描述了消费需求不⾜和投资需求不⾜导致的经济相对过剩和有效需求不⾜。
认为市场经济机制无法⾃动调节恢复到充分就业均衡状态，需要外部干预。
文章为理解不同类型的经济增⻓模式提供了理论框架，并通过分析各种模式的特性和限制，展示了经济增⻓的多样性和复杂性。
大 纲
回望经济理论描述的“经济增长”类型，大致可分为四种。
第一种是“斯密型增长”
经济运动的这种增长来自“斯密动力(Smithian Dynamics)”的推动。
它以各行各业的比较优势为基础，通过专门化专业化的分工，伴随资本投入扩大和市场规模延伸而得以推进。
而得到结果：通常是国民经济产出总量和人均产量均同时增长。这样的增长可看成是水平延拓型增长，用一个不那么合适的比喻来说，相当把一块限定体积面团进行“摊大饼”。
斯密型增长所能达到的终极规模，受分工精细到极致（分工的终极形态是形成一个个独立的企业，即分工不会形成以劳动个体性质的单位，在分工形成过程的其中某个阶段，就被由诺贝尔奖获得者科斯首提的“交易费用”所阻断），资本投入到溢出，以及触及极端的“毛细管”市场而终止！
对于斯密型增长达到的极限状态，经济学已有十分成熟的新古典经济学理论予以认证和刻画。粗糙的是以文字阐述的萨伊理论——供给自行产生需求。精致的是以数学集合论为基础推导的一般均衡论——完全竞争市场状态下的经济静态均衡。
第二种为“熊彼特型增长”
熊彼特型增长，亦由“熊彼特动力(Schumpeterian Dynamics)”所形容的——通过发挥企业家精神，借助“创造性破坏”力量，形成生产要素配置不断创新，促进生产要素技术的持续进步、实现经济的集约化和可持续增长，使生产总量与人均产出不断同时增长。
熊彼特型增长，不但仍包含斯密式增长——水平延拓型不断“摊大”面团，还具有垂直增高型面团发酵不断“膨胀”的特性，且其增长规模在长时期的观察视野内——随着时间的延续没有终极性的限制。
另外，熊彼特还以“创新非均匀性”为核心观点阐述了经济周期。
在分析中，假定“创新”之前经济处于静态均衡（可认为已是斯密增长的极限状态），企业的支出等于收入，企业或企业家没有超额利润。但企业家为获得超额利润（新产品价格（乘上产品数量）与生产要素价格（乘上各生产要素数量）之间的价值差额）而努力创新。当创新浪潮出现时，社会上对生产资料的需求扩大，这当然伴随银行信用的扩张，从而经济高涨。
不过当创新进一步扩展后，由于蜂拥而至模仿者的激烈竞争，使创新商品大大普及从而导致价格下跌，企业盈利机会减少，银行信用收缩。于是，经济从繁荣转入衰退。最终，熊彼特增长的暂停导致经济重新归宿于斯密均衡。如此循环往复。
这样，周而复始经济周期的表现就像被投石激荡的水面，先是“高耸深陷”的水浪，从中心往四周扩散的同时，波纹峰谷逐渐降低，渐渐衰变为微微起伏的涟渏，最终归复成静止如镜的水面。
第三种为“马尔萨斯型增长”
马尔萨斯发现以他命名的马尔萨斯机制：截止他生活的时代，几乎所有社会的人均生活水平都在温饱线上下波动，虽然经济总量仍然存在不断扩大的趋势，但是人均生活水平却没有伴随着的增长趋势。后人把这个现象称作“马尔萨斯陷阱”。
对这个现象，马尔萨斯也给了一个合理解释：经济产出总量增长的同时，但由于人口数量的更快增长，从而导致人均产量下降，即产量增长的速度赶不上人口增长的速度，从而总是坠入马尔萨斯陷阱的温饱线上。
马尔萨斯平衡，相当于不断增大的面团，但在人口擀面杖的重压下，总被“摊薄”为仅能保证温饱的某限定厚薄的一层。
我国学者吴乐旻在《富种起源:人类是怎么变富的》（北京：中信出版社，2023年2月）专著中提出一种新机制来解释马尔萨斯陷阱的形成机制。
下面是该书的主要观点：
人是社会性动物，人类不仅仅以个体形态生存，更是以组织化社会化形态生存繁衍。吴乐旻称后者形态为族群。比照达尔文描述生物在个体繁衍和群体繁衍中，资源不仅被用于个体与自然的争斗中，更有另一部分资源被用于择偶争斗中。吴乐旻认为，人类族群存衍所需产品，也可分类成个体生存之用的生存品和族群生存之用的效用品。个体生存之用的生存品用于“与外界自然的竞争”，而族群存衍之用的效用品被用于“人类内部竞争”！
个体和集体之间由生存繁衍导致的矛盾是产生效用品的根源。单单从孤立族群生存繁衍角度看，效用品是一种“囚徒困境”式如同“军备”竞赛的无谓损失。但从地球上从来就存在多个族群竞争生存繁衍的角度分析，它却是必不可少的。
从而，人类的整体存衍过程中必须得有两个部门的协调生产，一个部门生产生存品，另一个部门生产效用品。而马尔萨斯学说则是舍弃了效用品部门的生产后，仅仅针对生存品单部门模型在极端假设下的那种特殊情形。
正因为吴乐旻的生存品和效用品双部门模型考虑了发生在族群存衍斗争中的竞争和选择，所以他的理论能够在容纳更多因素而于更大范围的框架内，解释图1 中世界人均收入变化中出现的那些起伏波谷，比如古希腊城邦、古罗马帝国、中国两宋皇朝等相比其余时期所具有相当发达的经济水平。
当然，进一步的发挥还可以解释工业革命以来世界经济的巨大增长。
史载以来，人类社会出现过古希腊、古罗马、中国两宋这样市场已成规模，但科技进展缓慢的文明——现时人们可以认为，显然这些都是斯密式的市场增长，缺乏熊彼特式的科技革新。在这些社会的后期，随着条件的改变，物产流通从昌盛变为停滞，市场规模由兴盛归之萎缩，经济总量和人均收入都归于衰退。所以重又陷入马尔萨斯陷阱中。
而起源于英国的工业革命则是一股延续至今的以科技进步为主导，以熊彼特式增长为主、斯密式增长为辅的增长浪潮。
第四种增长是凯恩斯增长
凯恩斯创建宏观经济的理论基础，是从大量经验事实中归纳的三个“基本的心理因素”，即：“消费倾向”，“对资本资产未来收益的预期”和“现金流动偏好”。
“消费倾向”心理因素决定了人们对于消费产品的需求。凯恩斯认为，随着人们收入的增加，用于增加消费的那部分需求逐渐减缓。所以，一国经济总量中被用于消费的部分，必将随着一国经济总产出的不断增加，份额不断下降，从而，总产品中不能被消费吸收而被“强制”储蓄的份额和绝对值都不断增加。这就引起了消费需求不足。
而“对资本的未来收益预期”心理因素决定于“资本的边际效率”。由于不断增加的“强制”储蓄部分，被转化成越来越大的投资规模，导致资本边际生产力不断递减。资本边际效益的不断下降，必然引起实物利息率的下降。
“现金流动偏好”是指人们愿意用货币形式保持自己的收入或财富这样一种心理因素，它决定了人们愿意持有货币的意愿或需求。在一定的货币供应量下，“资本的边际效率”同“现金流动偏好”一起，加上一国货币的存量，三者综合作用同时决定了货币的利息率和人们愿意用货币形式保留自己的收入和财富。
据此凯恩斯推导：当随着生产规模的持续扩大，被用于消费部分的产品由于必然出现的消费需求不足而无法被完全消费。而这些产品被“强制”储蓄后，转而形成被用于再生产的投资部分，也由于投资需求不足而无法用去。两者的共同作用，无法使得生产规模达到它本应有的规模。
从而，经济运行结果一般地总是处于于社会总生产能力的下方。
这样的宏观理论叙述的结论就是：市场经济机制的自行运转，必然使得社会经济在未达到新古典经济学所论证的充分就业均衡之前，就形成了生产供给相对过剩、有效需求相对不足的尬尴均衡，导致大量失业存在。从而，凯恩斯得出结论，自由放任的市场经济机制无法让经济自动调节恢复到充分就业的均衡状态。
概括凯恩斯宏观经济学的精髓就是：经济均衡总量由“被动”储蓄量等于“主动”投资量瞬间的那一个值决定。
这样一来，经济体系的均衡总量是一系列可能的点，而一般均衡经济理论假定的充分就业时的均衡总量，仅是所有可能均衡位置的上极限。从而一般地，经济均衡总停留在非充分就业状态上。
如果对这样的经济运行进行评价的话：“这样的经济运行不但是相对过剩的，而且是平衡的，并且还是平静的。”
这就是凯恩斯平衡，它似乎像是那块恒定体积的面团，本应该可以摊成一张更大的斯密型大饼，但由于“三大心理定律”使经济体系产生“蠕动”回缩，再是怎么擀薄，面饼总是无法达到本应有的那么大。
Four Types of Economic Growth and Equilibrium
Looking back at the types of "economic growth" described in economic theories, they can be roughly divided into four categories.
The First Type: "Smithian Growth"
This kind of economic growth comes from the impetus of "Smithian Dynamics".
It is based on the comparative advantages of various industries. Through specialized division of labor, accompanied by the expansion of capital investment and the extension of market scale, it is promoted.
And the result is usually that both the total output of the national economy and the per capita output increase simultaneously. Such growth can be regarded as horizontal extension growth. To use a not-so-appropriate metaphor, it is quite like "spreading out a flat cake" with a dough of a limited volume.
The ultimate scale that Smithian Growth can reach is terminated by the extreme refinement of the division of labor (the ultimate form of the division of labor is the formation of independent enterprises, that is, the division of labor will not form units in the nature of individual laborers. At a certain stage in the formation process of the division of labor, it is blocked by the "transaction costs" first proposed by Coase, the Nobel Prize winner), the overflow of capital investment, and reaching the extreme "capillary" market!
For the limited state reached by Smithian Growth, there are already quite mature neoclassical economic theories in economics to verify and describe it. The rough one is Say's theory described in words-supply creates its own demand. The refined one is the general equilibrium theory derived based on the mathematical set theory - the static equilibrium of the economy under the condition of a perfectly competitive market.
The Second Type: "Schumpeterian Growth"
Schumpeterian Growth is also described by "Schumpeterian Dynamics" - by giving play to the entrepreneurial spirit and relying on the power of "creative destruction", it forms continuous innovation in the allocation of production factors, promotes the continuous progress of production factor technology, realizes the intensive and sustainable growth of the economy, and makes the total production and per capita output increase simultaneously.
Schumpeterian Growth not only still includes Smithian Growth - continuously "spreading out" the dough in a horizontal extension way but also has the characteristic of the dough "swelling" like fermentation in a vertical heightening way. And its growth scale has no ultimate limit within the long-term observation horizon - as time goes on.
In addition, Schumpeter also expounded the economic cycle with the core view of "innovation non-uniformity".
In the analysis, it is assumed that before "innovation", the economy is in a static equilibrium (which can be regarded as the limit state of Smithian Growth). The expenditures of enterprises are equal to their incomes, and enterprises or entrepreneurs have no excess profits. However, entrepreneurs strive to innovate in order to obtain excess profits (the value difference between the price of new products (multiplied by the quantity of products) and the price of production factors (multiplied by the quantity of each production factor). When the wave of innovation emerges, the demand for means of production in society expands, which is of course accompanied by the expansion of bank credit, and thus the economy booms.
However, as the innovation further expands, due to the fierce competition of the swarming imitators, the innovative goods are widely popularized, resulting in a price drop, a reduction in the profit-making opportunities of enterprises, and the contraction of bank credit. As a result, the economy shifts from prosperity to recession. Eventually, the suspension of Schumpeterian Growth causes the economy to return to Smithian equilibrium again. And this cycle repeats itself.
In this way, the performance of the economic cycle that repeats itself is like the water surface stirred by a stone. First, there are "high and deep" water waves. While spreading from the center to the surroundings, the peaks and valleys of the ripples gradually decrease, gradually fading into slightly undulating ripples, and finally returning to a still water surface like a mirror.
The Third Type: "Malthusian Growth"
Malthus discovered the Malthusian mechanism named after him: By the time he lived, the per capita living standards of almost all societies fluctuated around the subsistence line. Although there was still a tendency for the total economic output to continue to expand, the per capita living standards did not show a corresponding growth trend. Later generations called this phenomenon the "Malthusian Trap".
For this phenomenon, Malthus also gave a reasonable explanation: While the total economic output is growing, due to the faster growth of the population, the per capita output decreases. That is, the growth rate of output cannot keep up with the growth rate of the population, so it always falls into the subsistence line of the Malthusian Trap.
The Malthusian equilibrium is equivalent to a constantly growing dough, but under the heavy pressure of the "population rolling pin", it is always "spread thin" into a layer with a certain limited thickness that can only guarantee subsistence.
Our scholar Wu Lemin put forward a new mechanism in his monograph "The Origin of Wealth: How Humans Became Rich" (Beijing: CITIC Press, February 2023) to explain the formation mechanism of the Malthusian Trap.
The main viewpoints of this book are as follows:
Human beings are social animals. Humans not only survive in an individual form but also survive and reproduce in an organized and socialized form. Wu Lemin calls the latter form an ethnic group. Comparing with Darwin's description that in the reproduction of individuals and groups of living organisms, resources are not only used in the struggle between individuals and nature but also another part of resources are used in the struggle for mates. Wu Lemin believes that the products needed for the survival and reproduction of human ethnic groups can also be classified into survival goods for individual survival and luxury goods for ethnic group survival. Survival goods for individual survival are used for "competing with the outside nature", while luxury goods for ethnic group survival are used for "human internal competition"!
The contradiction caused by survival and reproduction between individuals and collectives is the root cause of the emergence of luxury goods. From the perspective of the survival and reproduction of isolated ethnic groups alone, luxury goods are a kind of unnecessary loss like an "arms race" in the form of a "prisoner's dilemma". But from the perspective of the existence and reproduction competition of multiple ethnic groups that have always existed on the earth, it is essential.
Therefore, in the overall process of human survival and reproduction, there must be coordinated production in two sectors. One sector produces survival goods, and the other sector produces luxury goods. And the Malthusian theory is the special case under extreme assumptions of a single-sector model that only focuses on survival goods after abandoning the production of the luxury goods sector.
Precisely because Wu Lemin's two-sector model of survival goods and luxury goods takes into account the competition and selection in the struggle for the survival and reproduction of ethnic groups, his theory can explain the fluctuations and troughs in the changes in the world's per capita income shown in Figure 1 within a framework that accommodates more factors and in a larger scope, such as the relatively developed economic levels of the ancient Greek city-states, the Roman Empire, and the Song Dynasty in China compared with other periods.
Of course, further elaboration can also explain the huge growth of the world economy since the Industrial Revolution.
From historical records, human society has witnessed civilizations such as ancient Greece, ancient Rome, and the Song Dynasty in China, where markets had already taken shape but technological progress was slow. Now people can think that obviously this was Smithian market growth, lacking Schumpeterian technological innovation. In the later periods of these societies, with the change of conditions, the circulation of goods changed from prosperity to stagnation, the market scale shrank from prosperity, and both the total economic output and per capita income declined. So they fell back into the Malthusian Trap again.
And the Industrial Revolution that originated in the UK is a growth wave that has continued until now, dominated by technological progress, mainly Schumpeterian Growth and supplemented by Smithian Growth.
The Fourth Type: "Keynesian Growth"
The theoretical basis for Keynes to create macroeconomics is three "basic psychological factors" summarized from a large number of empirical facts, namely: "propensity to consume", "expectation of the future yield of capital assets", and "liquidity preference".
The psychological factor of "propensity to consume" determines people's demand for consumer products. Keynes believed that as people's incomes increased, the part of the demand used to increase consumption gradually slows down. Therefore, the part of a country's total economic output that is used for consumption will inevitably decline in share as the country's total economic output continues to increase. As a result, the share and absolute value of the part of the total products that can not be absorbed by consumption and are "forced" to be saved are constantly increasing. This leads to insufficient consumer demand.
The psychological factor of "expectation of the future yield of capital assets" is determined by the "marginal efficiency of capital". Due to the increasing "forced" savings part being transformed into an increasingly large investment scale, the marginal productivity of capital continues to decline. The continuous decline in the marginal efficiency of capital will inevitably lead to a decline in the real interest rate.
"Liquidity preference" refers to the psychological factor that people are willing to keep their incomes or wealth in the form of money. It determines people's willingness or demand to hold money. Under a certain money supply, the "marginal efficiency of capital" together with the "liquidity preference", plus the stock of a country's currency, jointly determine the interest rate of money and people's willingness to keep their incomes and wealth in the form of money.
based on this, Keynes deduced that as the production scale continues to expand, the products used for consumption cannot be completely consumed due to the inevitable insufficient consumer demand. After these products are "forced" to be saved, they are then turned into the investment part used for reproduction, but they also can not be used due to insufficient investment demand. The combined effect of the two makes it impossible for the production scale to reach the scale it should have.
Thus, the result of economic operation is generally always below the total social production capacity.
The conclusion of such a macroeconomic theoretical narrative is that the self-operation of the market economic mechanism will inevitably lead to an awkward equilibrium of relative overproduction of supply and relative insufficiency of effective demand before reaching the full employment equilibrium demonstrated by neoclassical economics, resulting in a large number of unemployed people. Thus, Keynes concluded that the laissez-faire market economic mechanism cannot make the economy automatically adjust and restore to the full employment equilibrium state.
To summarize the essence of Keynesian macroeconomics: The equilibrium total amount of the economy is determined by the value at the moment when the "passive" savings amount is equal to the "active" investment amount.
In this way, the equilibrium total amount of the economic system is a series of possible points, and the equilibrium total amount at full employment assumed by the general equilibrium economic theory is only the upper limit of all possible equilibrium positions. Thus, generally speaking, the economic equilibrium always stays in a state of less than full employment.
If we evaluate such economic operation: "Such economic operation is not only relatively excessive but also balanced and calm."
This is the Keynesian equilibrium. It seems like that piece of dough at a constant volume, which should have been able to be spread into a larger Smithian flat cake, but due to the "three psychological laws", the economic system "creeps" and shrinks back. No matter how thin it is rolled out, the flat cake can never reach the size it should have.
