Price transmission of Vietnam's Robusta coffee : a thesis presented in partial fulfilment of the requirements for the degree of Master of AgriCommerce at Massey University, Palmerston North, New Zealand

Coffee is important to Vietnam’s economy in terms of export earnings and employment. As Vietnam carried out market reforms over the last three decades, its coffee sector has become increasingly market-driven and exposed to the fluctuations of the global market. The transmission of changes in global Robusta coffee prices to domestic farmgate prices is put under focus in this research as the knowledge of this will have important policy and welfare implications. This research uses both linear and threshold vector error correction models to analyse price transmission as the cointegration-based approach recognises the nonstationarity of price series. The data used are daily export and farmgate prices of Robusta coffee, measured in USD per tonne, from June 1st, 2011 to December 31st, 2015. Export prices were collected in Ho Chi Minh city, the export hub for Vietnam, and farmgate prices in the largest coffee-producing province, Dak Lak. The primary result of this research is that of a symmetric price transmission between export and farm levels for Vietnam’s Robusta coffee. The two apparent asymmetries detected are considered minimal as the speed of daily adjustment is too high. In the linear model, export prices react faster to negative deviations from the long run equilibrium than to positive deviations. In the threshold model, farmgate prices respond faster to decreases than increases in export prices when the long run deviation exceeds a certain threshold. The research also confirms the importance of transaction costs and other price frictions that were mostly ignored in prior analyses for coffee. Most importantly, the finding of symmetric price transmission contradicts previous studies which found asymmetric price transmission for Robusta coffee in Vietnam and other producers in Africa. This dissimilarity may be attributable to characteristic differences of Vietnam’s coffee sector, the use of high frequency data, and to the different time periods under investigation. JEL Codes: C32, Q11, Q13, Q17 Keywords: asymmetric price transmission, Robusta coffee, Vietna

Price Asymmetry of Coffee Beans: Evidence from Vietnam

The research evaluates the price transmission between export and farmgate prices for Vietnam’s Robusta coffee. Our findings suggest that minor asymmetry price transmission exists for export prices in the long-run and for farm prices in the short-run when thresholds are considered. Besides, the daily speed of adjustment is so high as to lead one to conclude that the price transmission is symmetric. Some possible explanations include the low concentration of local exporters, Robusta’s low quality, and coffee oversupply. Given the recent downward trend in global coffee bean prices, this result also implies that liberalisation current policies are inadequate to ensuring coffee farmers’ welfare

Testing vertical price transmission for Vietnam’s Robusta coffee

Vietnam has undergone market reforms over the last three decades; and as a consequence, the coffee sector has become increasingly market-driven. The success of the government’s liberalisation policies in terms of market efficiency is investigated by examining the transmission of both positive and negative price changes for Robusta coffee between export and farmgate prices. We used a threshold vector error correction model and high-frequency daily data. The primary result here is that of a symmetric price transmission between export and farm-level prices. This result holds when tested with weekly price data, derived from the daily data. Farmgate prices respond faster to decreases than increases in export prices when the long-run deviation exceeds a certain threshold. These price changes are transmitted within several days. This research also confirms the importance of transaction costs, and other price frictions mostly ignored in prior analyses for coffee

Characterization of ionospheric irregularities over Vietnam and adjacent region for the 2008-2018 period

International audienceThis paper presents the variations of the rate of change of Total Electron Content (TEC) index (ROTI), characterizing the occurrence of ionospheric plasma irregularities over Vietnam and neighboring countries in the Southeast Asian region using the continuous GPS data during the 2008-2018 period. The results showed that the occurrence of strong ROTI in all stations is maximum in equinox months March/April and September/October and depends on solar activity. The ROTI is weak during periods of low solar activity and strong during periods of high solar activity. There is an asymmetry between the two equinoxes. During maximum and declining phases of 2014-2016, occurrence rates in March equinox are larger than in September equinox, but during the descending period of 2010-2011, the occurrence rates in September equinox at almost all stations are larger than in March equinox. The correlation coefficients between the monthly occurrence rate of irregularities and the F10.7 solar index at the stations in the equatorward EIA crest region are higher than at those in the magnetic equatorial and the poleward EIA crest regions. The irregularity occurrence is high in the pre-midnight sector, maximum between 2000 LT to 2200 LT. The maximum irregularity occurrence is located around 4-5° degrees in latitude equator-ward away from the anomaly crests

Ionospheric quasi-biennial oscillation of the TEC amplitude of the equatorial ionization anomaly crests from continuous GPS data in the Southeast Asian region

International audienceThe quasi-biennial oscillation (QBO) signals at two Equatorial ionization anomaly (EIA) crests of the ionosphere have been studied using the continuous GNSS network data in Vietnam and adjacent regions during the 2008- 2021 period. The monthly mean EIA crests amplitudes are calculated. The Lomb-Scargle periodogram method was applied to the residuals of the EIA crests magnitudes, DTEC, which are obtained from subtracting the fittings with solar index, F10.7. The Lomb-Scargle spectrum shows the quasi-biennial component in the residuals DTEC with the picks at 18, 25, and 29-30 months. The ionosphere QBO at two EIA crests was found out by the band-pass filter centered at 25 months with haft-power points at 17 and 33 months. The zonal wind data at 50 hPa (~ 20 km) of the tropical equatorial stratosphere is used as the stratosphere QBO (SQBO) to consider the relationship between the SQBO and the obtained ionosphere QBO. The direct comparison and the cross wavelet transform of the SQBO and ionosphere QBO data series show that during 2008-2009, the ionosphere QBO signal is low, the SQBO and ionosphere QBO are in phase during the 2010-2013 and 2018-2021 periods, but anti-phase during the 2014-2017 period. For the 2010-2013, 2014-2017 and 2018-2021 periods, the correlation coefficients are 0.623, 0.637, -0.646 in the northern crest, and 0.571, 0.53, -0.530 in the southern crest, respectively. Furthermore, we also observed that the SQBO and the ionosphere QBO signals were shortened during the 2015-2016 period, approximately 1.5 years. Previous studies showed that the ENSO (El Niño - Southern Oscillation) warm phase, also known as El-Niño existed during 2015-2016. The results of this study allow us to assume that the SQBO influences the ionosphere QBO. Our results show that the SQBO is the main factor affecting the ionospheric QBO at two EIA crests. However, the physical theoretical interpretation of the mechanisms of action is a challenge for scientists and requires further research

Contemporary movement of the Earth's crust in the Northwestern Vietnam by continuous GPS data

The paper presents an estimation of the Earth’s crustal motion from the continuous GPS data at 6 stations (MTEV, MLAY, DBIV, TGIV, SMAV and SLAV) in the Northwestern and at PHUT (Hanoi) station using GAMIT/GLOBK software. The absolute displacements of the Earth’s crust at 7 stations in the IGS14 frame are respectively: 34.10±0.71 mm/yr (DBIV), 34.31±0.65 mm/yr (PHUT), 34.51±0.75 mm/yr (SMAV), 34.55±0.80 mm/yr (MLAY), 34.80±0.72 mm/yr (TGIV), 34.93±0.99 mm/yr (SLAV) and 35.59±0.73 mm/yr (MTEV), in the southeastward with the azimuth range 104-108o.  The Son La fault is a right-lateral slip fault with a shear amplitude of ~1.5 mm/yr. The Lai Chau-Dien Bien fault is a left-lateral slip fault with a shear amplitude of ~1.9 mm/yr. Although the absolute velocities at the DBIV, SMAV, SLAV, TGIV and MLAY stations are evaluated with the error <1 mm/yr, the relative displacement on the Ma River fault is of ~0.5 mm/yr, and it seems that we still do not have a reliable assessment of the slip rate on the Ma River right-lateral slip fault

BƯỚC ĐẦU NGHIÊN CỨU TỪ CẢM TRONG TRẦM TÍCH TẦNG VĂN HÓA HANG C6-1 Ở CÔNG VIÊN ĐỊA CHẤT TOÀN CẦU UNESCO ĐẮK NÔNG

The magnetic susceptibility (MS) of cave sediments has become a proxy for the paleoclimate. The magnetic properties of the sediments formed outside the cave are influenced by the weather. The sediments are later brought into the cave by various means and deposited. Thus, the MS in the stratigraphic column of cave sediments carries information about the weather when the sediments formed. The stratigraphic column at cave C6-1 has been investigated in several archaeological studies. In this study, 185 soil samples were collected to a depth of 184 cm at a sampling interval of about 1 cm. MS measurements were carried out by the Department of Geomagnetism at the Institute of Geophysics of the Vietnam Academy of Science and Technology. The MS results can be divided into eight magnetic zones, C6.1-1 to C6.1-8, of which C6.1-1, C6.1-3, C6.1-5, and C6.1-7 correspond to cold dry weather, and C6.1-2, C6.1-4, C6.1-6, and C6.1-8 correspond to warmer weather. Multi-Taper Method (MTM) analysis of the MS data shows three significant cycle ranges with MTM confidence levels above 95%. Using the carbon-14 radiocarbon dating method, we determined ages for three weather cycles of 562, 375, and 281 years. From 6,768 to 6,954 years BP, there was a sudden accumulation rate of sediment in the section that was 5 to 30 times higher than in other periods.Tham số từ cảm trong hang động đã trở thành một đai diện để đánh giá cổ khí hậu là do: Độ từ cảm trong các trầm tích được tạo ra bên ngoài hang chịu ảnh hưởng của quá trình hoạt động của thời tiết gây ra sự biến đổi thuộc tính từ của nó. Các trầm tích sau đó được đưa vào hang bằng nhiều cách và lắng đọng lại. Độ từ cảm trong cột địa tầng này sẽ mang thông tin về thời tiết khi nó hình thành. 185 mẫu từ cảm (mỗi mẫu cách nhau 1cm) được thu thập dọc theo chiều sâu 184 cm mặt cắt đã có các nghiên cứu về khảo cổ tại hang C6.1 Đăk Nông. Các phép đo từ cảm được tiến hành tại phòng Địa từ, viện Vật lý Địa cầu. Kết quả MS được phân chia thành 8 vùng từ, lần lượt là C6.1-1 đến C6.1-8. Trong đó vùng từ C6.1-1, C6.1-3, C6.1-5, C6.1-7 tương ứng với thời tiết lạnh khô, còn các vùng từ C6.1-2, C6.1-4, C6.1-6, C6.1-8 tương ứng với thời tiết ấm hơn. Phân tích Fourie số liệu từ cảm cho thấy có 3 dải chu kỳ có ý nghĩa với độ tin cậy MTM trên 95%. Dựa trên bộ số liệu tuổi tuyệt đối đo được (C14) chúng tôi ngoại suy và xác định được khoảng tuổi của mặt cắt nghiên cứu là 2.200 năm và 3 chu kỳ thời tiết đồng thời xảy ra trong giai đoạn này là: Kỳ 562 năm, 375 năm và 281 năm. Trong khoảng mặt cắt nghiên cứu giai đoạn 6,768 – 6,954 năm BP lượng mưa lớn đột ngôt gấp 5 đến 30 lần so với các khoảng thời gian khá

Monitoring of Antibiotic Residues in Aquatic Products in Urban and Rural Areas of Vietnam

Antibiotic residues in aquatic products in Vietnam were investigated. A total of 511 fish and shrimp samples were collected from markets in Ho Chi Minh City (HCMC), Thai Binh (TB), and Nha Trang (NT) from July 2013 to October 2015. The samples were extracted with 2% formic acid in acetonitrile and washed with dispersive C18 sorbent. Thirty-two antibiotics were analyzed by LC-MS/MS. Of the 362 samples from HCMC, antibiotic residues were found in 53 samples. Enrofloxacin was commonly detected, at a rate of 10.8%. In contrast, samples from TB and NT were less contaminated: only 1 of 118 analyzed samples showed residues in TB and only 1 of 31 showed residues in NT. These differences were attributed to the local manufacturing/distribution systems. To understand the current status of antibiotic use and prevent adverse effects that may be caused by their overuse, continual monitoring is required