Impacts of Trade Protection by Tariffs on Agricultural Imports and Exports by Using GTAP Model: A Case Study in Vietnam

International economic integration has brought high growth to international trade while promoting economic development for many countries around the world. However, in recent times, in the world, there has appeared a trend opposite to trade liberalization, which is protectionism. Advocates for trade protection provide arguments for why countries implement trade-restrictive measures. Those causes are related to national security and defense, solving the trade deficit, creating jobs, protecting the nascent industry and ensuring fair trade. Countries are currently using tariff measures including import and export tariffs, and non-tariff measures. The article studies protectionism, analyzes the impact of trade protectionism by tariffs on Vietnam’s GDP and exports, and makes policy recommendations for the Government of Vietnam.

great again". The United States is ready to bring protectionism back and disrupt the long-standing international trade order. Many countries such as the EU, Japan, etc. have adjusted their trade policies to adapt to the changes of the US. This will set a precedent for the behavior of other countries in the future and reduce the role of the WTO as well as other multilateral economic and trade mechanisms. At the same time, the move to tighten protectionist measures as part of the "America First" campaign could lead to an increase in trade retaliation, even triggering a trade war on a global scale.
If the US-China trade "war" continues to drag on, it will strongly increase trade protectionism with limited state intervention policies in the economy and globalization. Therefore, the article analyzes the changes in US tariff policy affecting some economies in the world, and especially the Vietnamese economy. The article studies protectionism, analyzes the impact of trade protectionism of USA by tariffs on Vietnam's GDP and exports, and makes policy recommendations for the Government of Vietnam.

Literature Review
Trade protectionism is the foreign trade policy of countries aimed at using measures to protect the domestic market from fierce competition from imported goods on the one hand, and on the other hand to help the State support businesses in the domestic market and expansion into foreign markets (Balassa, 1965). According to Nguyen Mai (2018) and Amadeo (2018), trade protectionism is an economic term, referring to the application of measures to protect the country's production of goods (or services) against competition from other economies around the world.
In favor of trade protectionism, Demir and Sepli (2017) and Amadeo (2018) point out protectionist policies: Applying tariffs on imported products and thereby increasing the prices of imported goods causes they become less competitive than domestic goods. Research by Olga Solleder (2013) and Pham Sy Thanh (2019) on the trade effects of export taxes, based on a new data set of tax rates at the product level, estimates the trade-distorting effects of export taxes. The results, based on a theoretical fit estimate of the structural gravity model, indicate that the export tax burden is shared by exporters and importers and that export taxes play a role in the increase of world prices. Export taxes are associated with a significant reduction in trade, especially when applied to the extractive industries. Research by Antoine Bouët and David Laborde Debucquet (2010) on the economics of export taxes in the context of a food crisis focuses on assessing the reasons for using export taxes, especially in the context of a wage crisis. The study summarizes the effect of export taxes using both partial and general equilibrium theoretical models. Research by William Deese, John Reeder (2007) examines the issue of export taxes on major commodities. It is clear that 40 countries in the world have imposed export taxes in recent years.
Research by Aradhna Aggarwal (2004) quantitatively assesses the likely changes in market access opportunities for Indian exports due to US tariff reductions. The study identifies products specific to India at the ISIC 4-digit breakdown level, which can be considered tariff sensitive. Regression analysis 3 www.scholink.org/ojs/index.php/rem Research in Economics and Management Vol. 6, No. 4, 2021 on the relationship between the MFN tariff rate and India's exports to the US was used to quantitatively assess the impact of a possible tariff reduction in the Doha Round. This analysis shows that tariff cuts are hardly expected to benefit Indian exports to the US. With the full implementation of the tariff reduction roadmap, the increase in India's exports to the US will amount to 1.2 or 0.6 depending on the value of the B factor in the formula. These findings are most likely due to the tariff-sharing effect of NAFTA preferences in favor of suppliers in Mexico, a country that competes in many traditional commodities.
Research by Olga Solleder (2013) shows that export taxes are associated with a significant reduction in trade, especially with the horticulture and extraction industries. According to the author, the welfare implications of an export tax depend directly on the market power of countries and whether they are exporters or importers of the goods being taxed. The welfare impact on exporters without market power is ambiguous and depends on the elasticity of supply, demand, and substitution. Furthermore, reductions in taxing on exports may under certain conditions be welfare-enhancing if achieved through the achievement of relevant public policy objectives, e.g. value added, increase domestically, outpacing losses associated with falling exports. Exporters with market power clearly benefit because they can apply welfare-optimizing tariffs, place the tax burden on importers, and enjoy better trade terms. Fugazza and Molina (2011) use the time required to export as a proxy for export costs and import as a proxy for import costs, investigating the impact of per-period fixed costs to the duration of trade relationships by employing survival analysis. He also mentioned that higher tariff rates accompany lower hazards for the duration of trade relationships because of less competition for incumbent firms; this result is also in line with Besedeš and Prusa (2006b). In other words, they evidence the significant positive relationship between tariff rates and durations of trade relationships.
Similarly, according to Antoine Bouët and David Laborde Debucquet (2010), to limit the impact of export taxes, trading partners can respond by either reducing import duties or increasing export duties, depending on the situation. They are either net importers or net exporters of goods. The results also show that there is an important asymmetry between net exporters and net importers of an agricultural commodity during a food crisis, as net exporters can benefit from increase in world prices while net importers are hurt and unable to retaliate effectively.
Research by Hertel, T, W (1999)  to gain benefits in some cases and lose them in others. When the tariffs apply only to soybean products, the EU suffers a small loss in economic welfare; If tariffs were applied to all food imported from the US, the EU would see a modest increase in economic welfare (EU, 2019). The rest of the world has a welfare benefit in any case as some of these countries also export soybeans. From these conclusions, in 4 www.scholink.org/ojs/index.php/rem Research in Economics and Management Vol. 6, No. 4, 2021 order to promote exports, the solution drawn is still: (1) to choose export products with great competitiveness or need to improve the competitiveness of export products; and (2) diversify export markets.
Chin-Ho Lin (2015) explores the links between imported trade relationships, duration, and tariff rates.
We investigate how the probability of survival of trade relationships affected due to the difference in the tariff rates based on survival analysis. Using ASEAN+6 as the reporter with 89 trading partners on manufactured goods from 1996 to 2011. A series of findings are as follows. First, low-tariff trade survives longer than high-tariff trade on manufactured goods. Second, a significantly negative correlation between tariff rates and duration is evidenced, which increases around 4% hazard ratios.
Also, the reduction of tariff rates in intra-regional trade is helpful to prolong the length of trade relationships. Third, low tariff rates have 9.1% lower hazard ratios. The paper also obtains robust results in production networks and Rauch product's classification. Finally, the paper shows these findings could be the references for other economic organizations, which is aimed at the diminution of tariff rates.
Thus, there are many studies that support or oppose trade protectionism, especially the tariff instrument has a great impact on exporting countries of competitive products. Currently, there have not been many research publications related to analyzing the impact of trade protectionism through tariff instruments on Vietnamese exports using the GTAP model. The next content of the article will describe the model and results of studying the impact of tariffs on Vietnam's exports and GDP using the GTAP model.

Introduction of GTAP Model
To quantify the economic impact of AKFTA, the paper uses the Global Trade Analysis Project (GTAP) model. This is a general equilibrium model developed by Hertel (1999) of Purdue University, USA and widely used in the world. With a database of many regions around the world, the model provides an analysis framework to assess the impact of policies and changes in the structure of resource distribution by identifying policy beneficiaries and affected entities (Dimarana & Dougall, 2002;Todsadee et al., 2012).  Tables (IOTs), and is supplemented by various international datasets as discussed below. In its tenth edition, the 5 www.scholink.org/ojs/index.php/rem Research in Economics and Management Vol. 6, No. 4, 2021 GTAP Data Base covers 121 countries and 20 aggregate regions of the world for each reference year.
GTAP 10 includes updated IOTs for 50 countries, reflecting new cost structures and sales dispositions for each sector. According to Angel et al. (2019), in terms of sectoral coverage, GTAP 10 considers 65 products and services (this is the third GTAP sector classification, GSEC3), up from 57 in previous versions (GSEC2). In broad terms, GTAP classifies agriculture, food, resource extraction, manufacturing, and service activities to describe all economic activities in each country. GTAP 10 has more manufacturing and services sectors than previous versions). There are three new sectors in manufacturing, namely: Chemicals, Pharmaceuticals, and Rubber products, that were previously aggregated as a single "Chemical, Rubber, and Plastics (crp)" sector. We also now distinguish the Electrical Equipment sector separately from other machinery. In terms of services, the Data Base now represents Accommodations and Food Services, Warehousing, Real Estate Activities, Education and Health Services, which were previously included in aggregated Trade, Other transport, Other business and Other government services sectors, respectively.
The GTAP Data Base tracks reconciled bilateral trade data between countries. These trade data must be reconciled because the initial data are not balanced, i.e world exports differ from world imports, and, as well, there are frequent discrepancies between countries' reported imports and what their partners report as exports. GTAP merchandise trade data is based on the United Nations Commodity Trade (UN-COMTRADE) Statistics and the reconciliation treatment has been updated for all reference years using a new consistent methodology. The Data Base also accounts for how traded merchandise is delivered across countries using estimates of international transport margins. In GTAP 10, we use estimates based on reported values from a large set of countries with a sizable set of trading partners.
This results in more variability of international transport margins by mode of transport (i.e., land, air and water) than in previous versions. The new estimates are based on data from U.S. imports of merchandise and North American Trans-border Freight Data, EUROSTAT trade data for European countries, and the Latin American Integration Association (ALADI) imports data (Nuno & Villoria, 2019).
According to Brockmeier (1996), the GTAP model has the following characteristics: First, representative consumers in each region or territory determine the amount of consumed goods, the level of savings, and the government spending to optimize the Cobb-Douglas utility function; and the government is part of the model. Second, representatives in each sector of each region or territory determine production inputs (land, capital, skilled and unskilled labor, natural resources) and intermediate goods (domestic goods and imported goods). Intermediate goods is disaggregated from the factor of production in the production function; therefore, its price does not affect production inputs.
Intermediate goods includes imported goods and domestically produced goods. Parameters of the elasticity of substitution are determined before being included in the model. Third, the prices of goods and production inputs are determined so as to keep the balance between demand and supply in the market. The GTAP model also has some disadvantages: The model is static, so it is not possible to 6 www.scholink.org/ojs/index.php/rem Research in Economics and Management Vol. 6, No. 4, 2021 analyze the transition between two equilibria. Without financial markets in the GTAP model, it cannot deal with issues related to exchange rates, interest rates, and inflation, as well as the effects of monetary policy.
By imposing taxes and subsidies on basic goods and inputs, the government creates the difference between the price that buyers pay and the price that producers get. Policy interventions are modeled in the form of: ad valorem taxes, taxes and subsidies or quantitative restrictions like in textile trade.
International trade links are included in the model through the replacement of Armington by goods that differ in the country of origin. Therefore, in the commodity market, buyers distinguish domestically produced products from imported products with the same use. Imported products differ in their regions of origin, leading to two-way trade between different regions for tradable products (Figure 1).

Figure 1. Multi Region Open Economy without Government Intervention
The global model is a CGE model with a multi-sector structure. The global model has its own characteristics, being a multi-region model that covers many countries in which: -The database is "global", i.e. based on I/O tables (or SAMs) of many countries (calibrated to ensure consistency and reduce differences in data collection time and sector division manners of each country). However, the model also has certain disadvantages: -Because the model's data is from many countries with differences in time and structure, the consistency are not high (though be calibrated).
-Since the global model is quite complex, it takes a lot of effort for users to understand and apply.
Basic inputs and semi-finished products are two types of production inputs. In each region, to produce a fixed volume of output, it is assumed that each industry uses a combination of both inputs to The ratio of government spending to income for each region is kept constant. Government spending is allocated to goods according to a Cobb-Douglas distribution function. Total expenditure on domestically produced good and imported goods is based on a combination method such as the allocation of household spending on this good. Investment in each region is financed by global savings.
Each sector contributes a fixed percentage of income to total savings. Total savings can be allocated in two ways. The first way is that the allocation to each region will increase by the rate of increase in total savings. The second way is that the investment will be amortized according to the relative return.
Regions with rising yields relative to the global average will receive a larger share of investment while regions with declining yields relative to the global average will receive a lower share of investment.
Each region has 5 types of production inputs, including 2 types of labor (skilled and unskilled), a homogeneous capital good, land and natural resources. In a typical closed model, the total supply of labor and land is fixed for each region, but capital can move across borders to equalize the rate of 8 With tax cuts in region s, qxs (exports from r to s) can increase, which means that output (qo) in region s will increase. The higher the export to output ratio and (SHRXMD) the higher the export growth rate (qxs), the higher the output. Depending on the magnitude and sign of changes in domestic consumption (qds) as well as the ratio of domestic consumption to output (SHRDM), output can increase or decrease.
Domestic consumption and the share of imports together with a change in imports (qxs) cause a change in output as described by the following equation for the equilibrium of industries: qo(i,r) = SHRDM(i,r) * qds(i,r) + sum(s,REG, SHRXMD(i,r,s) * qxs(i,r,s)) + tradslack(i,r); (where i: Sector; r: Region; s: Destination) In the above equation, the market price level will change to ensure that the change in real output equals the sum of the changes in domestic consumption and exports. Therefore, changes in the price and quantity of output can be explained by (1).
Equation (2) below establishes the relationship between the price of imported goods by region (pms) and the total price of imports (pim), total imports (qim) and exports by source (qxs). Elasticity of Armington (ESUBM) affects the degree of price effect on exports. The reduction of tax on goods imported from source r will reduce the price of goods imported from region r (pms). If source r is important in terms of total trade to region s, then the tariff reduction also reduces total imports (pim).
the price difference between the r and s regions relative to the total price in the s region will essentially produce a substitution effect, represented by the group in equation 2, multiplied by the ESUBM. Total imports into region s (qim) show us the domestic market penetration effect or the magnitude of the increase in total imports of region s. The variable ams (increase in imports due to changes in technology imported from region r into s) represents the change in technology in region r with the significance of increasing exports to region s. Although this can be interpreted and expressed in different ways for many different research purposes, this variable was not used in this study.
qxs(i,r,s) = -ams(i,r,s) + qim(i,s) -ESUBM(i) * [pms(i,r,s) -ams(i,r,s) -pim(i,s)] Value added in the GTAP model is an aggregate function consisting of many commodities or endowments-labor, land, capital and natural resources. Although most changes in added value (qva) and price (pva) are mainly due to changes in output (qo and pm), the demand for each factor is determined by qva then pva.
Equation (3) below shows this relationship. If the price of the avaliable goods (pfe) is higher than the price of the value added, the demand for this goods will be lower, assuming substitution elasticity 9 Published by SCHOLINK INC.
www.scholink.org/ojs/index.php/rem Vol. 6, No. 4, 2021 ESUBVA for the CES function unchanged. In addition, any increase in total value added will directly translate into an increase in demand for available goods. This is how the demand for labor or employment for each industry is established, for both skilled and unskilled workers. Technological change in the use of the basic factor i in industry j in the region r(afe) can have a negative or positive effect on demand for this factor through price. Changes in wages for both skilled and unskilled workers are directly affected by changes in overall output market prices (pm) as well as changes in taxes on labour.
qfe(i,j,r) = -afe(i,j,r) + qva(j,r) -ESUBVA(j) * [pfe(i,j,r) -afe(i,j,r) -pva(j,r)] (3) In this model, welfare is estimated via Equivalence Variation (EV). Welfare is broken down into different components; the most important is allocative efficiency, terms of trade and changes in capital goods prices necessary to maintain the investment-savings balance.
Simulation description: Shock, close and result. To close the model, we assume full employment, perfect competition, and equilibrium in all markets. The outcome of the GTAP model should not be seen as annual growth but as a change over a period of several years.

Analysis of the Impact of Tariffs on Vietnam's Imports and Exports according to the Gtap Model
In analyzing models and recommending policies, the article focuses on analyzing the impact of US tariffs on Vietnamese exports to the US, mainly agricultural exports. This is because Vietnam's agricultural exports to the US and Europe account for a large proportion, which is vulnerable when the US imposes import tariffs.

Impact of tariffs on the export of Vietnamese goods in general on the US, EU, and China
Calculations using the GTAP 10 model show that the US increase of 5% import tax on all goods from Vietnam will sharply reduce exports to the US (  Table 2 shows the impact of the US increasing 5% import tax on goods that Vietnam imports from some markets of China, the US and the EU. Contrary to the export trend, the fact that the main export market is the US, increasing import tax on Vietnamese goods not only reduces Vietnam's imports from the US but also reduces Vietnam's imports from other countries such as China and the EU. The reason may be that Vietnam has to import most of its intermediate inputs and raw materials from abroad to produce exports. Therefore, an increase in import tax on Vietnamese goods will also reduce the import of Vietnamese goods. Groups of goods imported into Vietnam falling sharply include: rice, meat and 10 www.scholink.org/ojs/index.php/rem

Impact of tariffs on imports of foreign goods into Vietnam
Research in Economics and Management Vol. 6, No. 4, 2021 livestock, utilities, construction, transportation, communication and other services. The group of imported goods with little impact is heavy industry. Source: Author's caculations based on GTAP model.

Impact of Tariffs on Vietnam's Agricultural Exports to the US, EU and China
According to the most updated data from the GTAP10 model, Vietnam's rice export tax to the EU market is very high (39%), then to Southeast Asia and Africa (nearly 5%). Meanwhile, import tax from the US and China is 0%. Grains and other crop products have relatively low tariffs in the US, China and EU markets, while they are very high in South Asia and East Asia. The two groups of meat and livestock and aquatic products have import tax of 3.28% in the EU market, but are quite low in the US and China, although quite high in some other markets (South Asia and East Asia). With the current tax rates as above, the imposition of 5%, 10% and 15% tax rates on agricultural products will have an impact on Vietnam's exports to a number of markets as follows: For rice: Because the import price of the US and China for Vietnamese rice is at 0%, the imposition of import tax will negatively affect Vietnam's rice exports to these markets. The higher the tariff, the greater the drop in exports. Specifically, with the tax rate of 5%, 10% and 15%, Vietnam's rice exports to these two markets will decrease by 50.5%, 101% and 151.5%, respectively. Meanwhile, because the EU's import tax on Vietnamese rice is very high in the base scenario of 39% (2014 data), the imposition of import tax at 5%, 10% and 15 % will positively affect Vietnam's rice exports to the EU, with an increase of 247.16%, 210.86% and 174.55% respectively.

For the group of cereals and other crop products (except rice):
Since the import tax of the US, EU and China on these products of Vietnam is currently quite low, the import tax is imposed at 5 levels. %, 10% and 15% will negatively affect the export of this group of goods of Vietnam to the above markets.
Specific reductions are given in Tables 4 and 5.
For meat and livestock products: The US and China's import tax on Vietnam's meat and livestock products is quite low, at 0.5% and 0% respectively, while imports from the EU are higher (3.28% in the data reviewed). Therefore, the imposition of import tax will negatively affect Vietnam's seafood exports to the US and China, and seafood exports to the EU. Specific reductions are given in Tables 3   and 4.
For seafood products: Similar to meat and livestock products, the import tax of the US and China on Vietnam's seafood group is quite low, close to 0%, while imports from the EU are higher (3.6% in the data considered). Therefore, the imposition of import tax will have a very negative impact on Vietnam's seafood exports to the US and China, and seafood exports to the EU. Specific reductions are given in Table 4.

Impact of the US-China trade war on Vietnam's agricultural exports
The US-China trade war, although not directly affecting Vietnam's agricultural exports, can have an indirect impact through trade protection. As US agricultural products suffer heavy damage, the tendency to protect US agricultural products through measures such as export subsidies or import restrictions will tend to increase. Meanwhile, agricultural exports to China may benefit as China shifts to importing from other markets. In addition, there will be indirect effects through foreign income. As the US-China trade war tends to negatively affect global trade and economic growth, the demand for agricultural products in many countries may decrease.   and meat products to markets tend to increase slightly, possibly due to lower livestock input prices.
Other industries are not significantly affected.

Conclusions and Policy Recommendations
The context of trade protectionism is returning after the Covid-19 pandemic, the US-China trade war and the trend of increasing the application of non-tariff barriers, posing many potential risks to Vietnam's exports, especially especially in important markets such as the US, EU, Japan, and China.
The above context has brought Vietnam the risk of facing lawsuits and trade protection investigations, especially with seafood and agricultural exports. Therefore, in order to protect exporting enterprises against risks from trade protectionism, the State needs to take measures to support enterprises to raise their awareness and capacity to respond to non-tariff trade protection measures. In addition, strengthen the application of trade remedies to protect domestic production; to step up production in chains, 15 www.scholink.org/ojs/index.php/rem Research in Economics and Management Vol. 6, No. 4, 2021 standardize production processes, improve the quality and added value of exported products, to meet the requirements of importing countries; at the same time diversifying markets, promoting exports to other potential markets to achieve a more sustainable export demand. among WTO members. However, in order to enjoy the preferential tariff rates of the FTA, Vietnam's exports need to meet the rules of origin to determine the eligibility of imports to enjoy the preferential tax rates. Some of the main reasons why businesses have not taken advantage of tax incentives include: (1) Many businesses do not have a clear understanding of the rules of origin, or have not found a consultant; (2) Difficult to meet the rules of origin because the source of raw materials and accessories depends too much on a few sources outside the FTA; and (3) The procedures at the two ends of exportimport are not convenient, not enough to compensate for the costs that businesses spend to enjoy incentives… Therefore, so that Vietnamese businesses can make better use of them. tax incentives, especially in new generation FTAs.
Secondly, ensure the quality requirements of exported agricultural products to enjoy tax incentives in signed FTAs. The US-China trade war has affected the export of Vietnamese goods to the Chinese market in general and agricultural products. Due to difficulties in exporting to the US market, China has boosted domestic consumption. This makes Vietnamese goods not only compete with goods of other ASEAN countries but also compete with domestic goods of China. Therefore, the Chinese market has changed, it is no longer as easy as before. China introduces more and more strict and strict quality criteria, regulations and standards on food safety and traceability for imported goods, causing difficulties for Vietnamese goods. The tariff reduction to 0% for nearly 8,000 product lines under the ASEAN-China Free Trade Agreement is expected to create a "bump" for Vietnamese agricultural products to grow in exports to China. Therefore, to meet China's requirements to enjoy tax incentives, Vietnam needs to improve and standardize the production process of agricultural products for export, in addition to meeting the origin of goods.
Thirdly, reduce the risk of tax increases in foreign markets. The escalation of the US-China trade war due to trade protectionism and strategic competition between the two countries can help Vietnam 16 www.scholink.org/ojs/index.php/rem Research in Economics and Management Vol. 6, No. 4, 2021 benefit by filling the trade gap in the US after Chinese goods were imposed by very high tax rate in this market. In the context of the US increasing trade protectionism, the rapid increase of Vietnam's trade surplus with the US also makes Vietnam very easy to fall into the sights of US trade agencies. In the coming time, Vietnam needs to take appropriate countermeasures to avoid being included in the list of currency manipulators by the US in order to avoid trade remedies that the US may apply to Vietnam.
First of all, it is necessary to avoid exchange rate interventions that may be perceived by the United States as a currency manipulator. Changes in exchange rate policy could cause a deceleration in Vietnam's economy, as Vietnam is heavily dependent on exports, while exports are very sensitive to exchange rate fluctuations. In addition, both enterprises and state management agencies must take drastic measures to prevent the evasion of Vietnamese origin from foreign goods that have been mentioned in recent times. Enterprises need to strictly comply with regulations on certification of origin and not abet origin frauds and evade defensive measures. Agencies managing the agricultural sector also need to support businesses with information on how Vietnamese goods in their respective industries are being exported to other countries.
Fourthly, mitigate the impact of tariffs on economic growth and exports. The fact that countries increase trade protectionism in general has a negative effect on Vietnam's economic growth and exports, not only through measures to impose tariffs directly on Vietnam's exports, but also on indirectly through imposing tariffs on other countries, such as in the case of the US-China trade war, which reduces the demand for domestic agricultural products of the taxed countries. Therefore, to limit the negative impact of tariffs on Vietnam's economic growth and agricultural exports, it is necessary to boost exports to markets through other measures such as reducing trade and logistics costs. According to the World Bank (2021), tariffs account for only 1/14 of the average cost of trade, and most trade costs are incurred in transportation and logistics as well as cumbersome trade procedures and processes at the border and behind the border.

Funding
The article is part of the State-level project "Sustainable development of export of Vietnamese agricultural products in the context of trade protection" code ĐTĐLXH.02/20.