Judul: The Effect of Financial and Macroeconomic Performance on Stock Returns Before and During Covid-19 (Case Study of Animal Feed Companies on the Indonesia Stock Exchange)
Abstrak: Investment activity is one of the activities that can encourage economic growth. Investments can be made in the real sector and the financial sector. The livestock industry has good prospects in Indonesia to meet people's needs for animal protein. The animal feed companies with the largest production in Indonesia sequentially are PT. Charoen Pokphand Tbk (CPIN), followed by PT. Japfa Comfeed Indonesia Tbk (JPFA), PT Malindo Feedmill Tbk (MAIN), and PT. Sreeya Sewu Indonesia Tbk (SIPD), where the four companies were open and affected by Covid-19 which resulted in changes in their financial and share performance. On the other hand, there are movements in external factors (corn prices, soybean prices and the exchange rate are thought to be factors that play a role in the company's performance. This study aims to determine the company's financial performance, the impact of changes in external factors on stock returns, the relationship between internal and external factors on stock return performance The scope of this research is animal feed sub-sector companies listed on the Indonesia Stock Exchange in the period before and after Covid-19, namely from 2017 to 2021. The independent variables used in this study are Cash Ratio (CashR), Debt Equity Ratio (DER), Net Profit Margin (NPM), Inventory Turnover (ITO), exchange rates (exchange rates), international soybean prices, and local corn prices. While the dependent variable in this study is the stock price of animal feed companies. The analytical method used for this research is 1) panel data regression, 2) different test and 3) moderation regression. The results of the study show that the movement of the performance of the 4 companies fluctuated during the study period, especially at the beginning of the Covid period. The stock movement that occurs from the pattern shows that the exchange rates at the two companies (JPFA and MAIN) need to be considered because they provide different patterns. testing of internal and external factors with stock returns obtained some evidence of a significant relationship, namely NPM, CashR and DER while testing for moderation obtained two outputs that had a significant impact, namely NPM*LnKurs and CashR*LnKurs. There is a special note that NPM has different results before and during covid. Companies can still improve performance in general with the help of solvency. Where with solvability the company will have a cheaper cost of capital and efforts to increase business capacity are greater.
Keyword: Covid-19, External Factor, Feed Company, Internal Factor, Stock Return.

Judul: The Impact of Macroeconomic Variables and COVID-19 Pandemic On Stock Prices Of Agribusiness Companies in Indonesia
Abstrak: Penelitian ini bertujuan untuk mengetahui pengaruh faktor makroekonomi dan pandemi COVID-19 terhadap harga saham perusahaan agribisnis di Indonesia baik di hulu maupun hilir. Lima variabel makroekonomi (inflasi, kurs, suku bunga BI, harga minyak dunia, dan harga minyak kelapa sawit) digunakan sebagai variabel independen, pandemi COVID-19 sebagai variabel dummy dan harga saham perusahaan agribisnis sebagai variabel dependen. Data yang digunakan adalah data sekunder dari tahun 2015 hingga tahun 2020 dan dianalisis dengan ECM (Error Correction Model). Hasil penelitian menunjukkan bahwa dalam jangka pendek, hanya harga minyak dunia dan harga minyak kelapa sawit yang memengaruhi kinerja harga saham perusahaan kelompok hulu sedangkan pada kelompok hilir, seluruh variabel termasuk pandemi COVID-19 tidak memengaruhi kinerja harga saham perusahaan. Dalam jangka panjang, seluruh variabel termasuk pandemi COVID-19 memengaruhi kinerja harga saham perusahaan kelompok hulu sedangkan untuk kelompok hilir, hanya inflasi, kurs, harga minyak dunia, harga minyak kelapa sawit, serta pandemi COVID-19 yang memengaruhi kinerja harga saham perusahaan.
Keyword: agribusiness, stock prices, macroeconomic variables, COVID-19, ECM

Judul: Formulasi Hamiltonian untuk Menggambarkan Gerak Gelombang Soliter Dimensi Tiga di Permukaan Laut
Abstrak: Gelombang permukaan adalah gelombang yang terjadi perbedaan rapat massa antara air dan udara. Salah satu gelombang permukaan yang ditinjau adalah gelombang soliter. Formulasi gelombang soliter dilakukan dengan menggunakan formulasi Hamiltonian.
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