第五章 新新贸易理论
Introduction
‘old’ trade theory adopted modelling approaches that assumed away intra-industry trade for simplicity’s sake
Empirical evidence revealed that the bulk of world trade was exactly of the assumed-away kind (Grubel and Lloyd 1975).
Introduction
‘new’ trade theory incorporated imperfect competition and increasing returns to account for intraindustry trade.
modelling approaches adopted assumed away differences among firms for simplicity’s sake.
Recent empirical evidence shows differences among firms are crucial to understanding world trade. For example:
firm differences within sectors may be more pronounced than differences between sector averages,
most firms – even in traded-goods sectors – do not export at all.
See Bernard and Jensen 1995, 1999a,b, 2001; Clerides, Lach and Tybout 1998, Aw, Chung, and Roberts 2000, Eaton, Kortum, and Kramarz 2004; see Tybout 2003 for a survey（Self- selection effect and Learning- by- exporting effect）
Empirical evidence
Empirical evidence
Empirical evidence
Bernard and Jensen 1995
Empirical evidence
Bernard and Jensen 1995
Empirical evidence
Introduction
‘new new’ trade theory incorporated firm-level heterogeneity to account for the many of the new firm-level facts.
Two Branches:
Melitz (heterogeneous firms)
Antras (endogenous boundary
of the firm)
Melitz model
Melitz is Krugman (1980) model with 2 additional elements:
1) Heterogeneity with respect to firm’s marginal costs, and
2) Fixed market-entry costs that are added to the standard fixed cost of developing a new variety.
These additions lead to a surprisingly wide range of new effects.
Introduction
The main theoretical papers in Melitz branch are Bernard, Eaton, Jensen and Kortum (2003), Melitz (2003), Helpman, Melitz and Yeaple (2004), Bernard, Redding and Schott (2004), Bernard, Eaton, Jensen, and Schott (2003), Melitz and Ottaviano (2005), and Yeaple (2005).
Melitz Model
Melitz (2003)
On the demand side, there is a representative consumer with preferences:
where Ω denotes the measure of available products and σ = 1/ (1-ρ) > 1 is the constant elasticity of substitution.
（1）
Melitz Model
Consumers maximize (1) subject to the budget constraint
FOC：Demand function for a particular variety w:
Where，
（2）
（3）
Melitz Model
The supply side is characterized by monopolistic competition.
Each variety is produced by a single firm (index varieties byφ) and there is free entry into the industry.
The fixed cost is assumed identical across firms and we denote it by f .
Melitz Model
The marginal cost is assumed to vary across firms and is denoted by 1/φ
Firms with higher φ are therefore more productive, in the sense that they need to hire fewer workers to attain a given amount of output (higher φ can also be interpreted as higher quality)
Total Cost Function
（4）
Because
FOC：
Melitz Model
So higher productivity firms also charge lower prices，produce more output
and obtain both higher revenues r (φ) and higher profits p (φ):
（5）
（6）
（7）
Melitz Model
Prior to entry, firms face uncertainty as to how productive they will turn out to be.
firms pay a fixed cost consisting of fe units of labor after which they draw a productivity level φ from a known distribution with pdf g (φ) and associated cdf G (φ);
Melitz Model
after observing φ , the producer decides whether to exit the market immediately or start producing according to the technology in (4).
In every period, the firm faces a probability δ of exogenous exit, which is common across firms.
Melitz Model
Expected value of the firm:
from (7) and (8) that there is a unique threshold productivity φ such that v (φ) > 0 if and only if φ > φ*
（8）
（7）
Melitz Model
Melitz Model
Let μ (j) be the distribution of (active firms) productivities in the economy
Define the weighted average productivity measure:
（9）
Melitz Model
define average profits：
10
Melitz Model
From equation (10) that there are two effects：
An increase in φ*will increase the average productivity of the surviving firms
Because firm profits are decreasing in the productivity of rivals, there is also an additional effect that goes in the opposite direction.
Melitz Model
Free entry ensures that the expected discounted value of profits for a potential entrant equal the fixed cost of entry
(10) and (11) form a system of two equations in two unknowns.
（11）
Melitz Model
Melitz Model
we can now move to the open economy version of the model and analyze the exporting decision as well as the reallocation effects generated by trade.
Melitz (2003) introduces trade frictions. These are of two types:
A standard per-unit iceberg costs, so that τ units need to be shipped for 1unit to make it to any foreign country;
An initial fixed cost of fex units of labor to start exporting, which is incurred once the firm has learnedφ.
Melitz Model
Firms will charge constant markups in both domestic and foreign sales, so domestic revenues are:
where as revenues from foreign sales in country k are:
Melitz Model
The assumption of symmetry will imply that for all k,
So we can express firm revenues by export status as：
Melitz Model
The corresponding profit levels are，
We now have two relevant thresholds:
Melitz Model
Firms with φ〉φ* will remain in the market after learning their Productivity,while those with φ〉φx will not only produce domestically, but also export.
In equilibrium，
Melitz Model
Average expected profits as
The free entry condition
Melitz Model
Melitz Model
The impact of trade
The ZCP schedule in the open economy is an upward shift of the ZCP schedule under autarky.
Firms with productivity betweenφa* and φ*are not able to earn positive profits under trade.
Consistently with the findings in the literature, exposure to trade thus forces the least productive firms to exit or shut-down.
New source of gains from trade: Increased Average Productivity.
Pol Antras
More than 1/3 of world trade is intra-firm but almost none in the models
Some in Vertical MNC models
Stylised facts about intra-firm trade
Tends to be more important in K-intense goods
Antras uses ‘new theory of the firm’ from IO to endogenize the intra- vs inter-firm trade choice
Modelling seems strange to trade economists now.
参考文献
Antràs, Pol, (2003), “Firms, Contracts and Trade Structure,” QJE, 118(4), 1375-1418.
Antràs and Helpman, (2004), “Global sourcing”, JPE 112: 552-580.
Grossman, G. and E. Helpman, “Outsourcing in a global economy,” RES 2005, 135-159.
Spencer, Barbara, “International Outsourcing and Incomplete Contracts”, Canadian Journal of Economics,38(4) November 2005, 1107- 1135
Helpman (2006), “Trade, FDI, and the Organization of Firms”, NBER Working Paper 12091,
forthcoming in Journal of Economic Literature.
Helpman, Elhanan, Marc J. Melitz, and Stephen 2004, "Export versus FDI with heterogeneous firms", AER 94(1), 300-316.
Melitz, Marc, (2003), “The Impact of Trade on Intra-Industry Reallocations and Aggregate Industry Productivity,” Econometrica, Vol. 71, 1695-1725.
作业
简述新新贸易理论的新发展及其趋势
DATE OF BIRTH: June 30, 1975CITIZENSHIP: Spain (. Permanent Resident)
