Judul: Analysis of portfolio optimization with and without shortselling based on diagonal model: evidence from indonesian stock market
Abstrak: Markowitz (1952, 1959) and Roy (1952) proposed portfolio theory which narrate that risk of a portfolio is the variance of individual securities and covariances among those securities comprising the portfolio. The objectives of this research is to construct an optimized portfolio using Sharpe's diagonal model with and without short selling respectively, and to analyze the performance of less diversified optimal portfolios by investing in a single industry versus well diversified portfolio by investing across all industries. Finally to analysis the statistical properties of the estimates of diagonal model. Markowitz mean-variance portfolio optimization theory is implemented for all stocks listed in 9 sectors of Indonesian stock market during 2007-2011. However our model used 269 stocks which are not contradicting to the basic assumptions of the diagonal model. Diagonal model used in this research is a linear model and data used are time series secondary data. Firstly 9 optimal portfolios are computed for individual sectors with the assumption that short selling not permitted and then computation is done with assumption that short selling is permitted. Similarly 2 optimal portfolios are computed consisting of all stocks with assumptions mentioned above. Results showed that both well diversified short and long portfolios provide higher returns at a specified risk level compare to portfolios consist of individual sectors stocks. Largest weight in short portfolio is from infrastructure, utilities and transportation sector equaling 17.2 percent. Largest weight in long only portfolio are from trade, investment and services sector equaling 23.2 percent. The more diversified and larger portfolios provide better tangency portfolio. All stocks short and long portfolios performed better than any other individual sector portfolio. Standard error for and residual standard error for other portfolios are large compare to individual stocks indicating risk was not diversified away. Least square parameters estimates were not quite promising such as value of portfolio beta happened to be less than individual stocks as well as value of its coefficient of determination shows most of the systematic risk could not get eliminated as low values of R2 for portfolios shows that most of the variance in stock return as well as in portfolio return is not explained by market variance therefore unsystematic risk could not get eliminated despite of forming a portfolio encompassing all equities listed in Indonesian Stock Exchange as suggested by results of regression analysis.
Keyword: Diagonal Model, Diversification, Portfolio Optimization, Short Sales

Judul: Comparative Analysis of Optimal Portfolio Using Markowitz Model and Single Index Model Based on Value at Risk (VaR)
Abstrak: Investasi merupakan salah satu variabel penentu dan berpengaruh positif terhadap pertumbuhan ekonomi (PDB). Berinvestasi pada saham dengan kapitalisasi pasar besar akan meningkatkan pertumbuhan IHSG. IDX80 merupakan indeks yang terdiri dari 80 saham yang memiliki likuiditas tinggi, kapitalisasi pasar besar, dan fundamental perusahaan yang baik. Penelitian ini bertujuan untuk mencari kombinasi saham yang memenuhi kriteria dalam pembentukan portofolio optimal berdasarkan model Markowitz dan Single Index Model serta mencari kinerja portofolio optimal terbaik menggunakan Value at Risk. Penelitian ini menggunakan data harga saham bulanan, IHSG, dan suku bunga acuan BI7DRR periode Februari 2019–Februari 2022. Hasil penelitian menunjukan bahwa terdapat 17 kombinasi saham yang membentuk portofolio optimal Single Index Model dengan expected return sebesar 0,01882 dan nilai varian sebesar 0,002582 perbulan. Sedangkan portofolio optimal yang terbentuk dengan model Markowitz menghasilkan enam kombinasi saham, expected return dan varian masing-masing sebesar 0,002243 dan 0,003866 per bulan. Berdasarkan hasil perbandingan menggunakan Value at Risk, portofolio optimal menggunakan metode Single Index Model lebih baik dibandingkan dengan model Markowitz karena memiliki expected return tertinggi, varian terbaik, kemungkinan kerugian terendah, dan kinerja portofolio terbaik., Investment is one of the determining variables and has a positive effect on economic growth (GDP). Investing in stocks with large market capitalization will increase JKSE growth. IDX80 is an index consisting of 80 stocks that have high liquidity, large market capitalization, and good company fundamentals. This study aims to find a combination of stocks that meet the criteria in forming an optimal portfolio based on the Markowitz model and the Single Index Model also to find the best portfolio performance using Value at Risk. This study uses reports of monthly stock price, JKSE, and interest rates BI7DRR period February 2019– February 2022. The results show there are 17 stocks combination form the optimal portfolio of the Single Index Model with an expected return of 0,01882 and a variance value of 0,002582 per month. While the optimal portfolio formed by the Markowitz model produces six stocks combination, the expected return and variance are 0,002243 and 0,003866 per month, respectively. Based on comparison using Value at Risk, the optimal portfolio by the Single Index Model is better than the Markowitz model because it has the highest expected return, the best risk, the lowest possible loss, and the best portfolio performance.
Keyword: Single Index Model, Value at Risk (VaR), IDX80 Index, Optimal Portofolio, Markowitz Model

Judul: Definisi Kalsium Dan Fosfor Pada Sapi
Abstrak: Kalsium dan fosfor mempunyai peranan penting dalam beberapa proses faali tubuh. Fungsi utama kalsium adalah mengatur iri tabilitas neuromuskuler, kontraksi otot, pembekuan darah, kofaktor beberapa sistim enzim dan sebagai komponen penting dalam pembentukan tulang (Rechcigl, 1978). Fosfor adalah komponen utama ikatan energi tinggi yaitu ATP (Adenosin Tri Phosphate), merupakan komponen nukleoprotein, mengatur pH isi rumen dan sebagai sumber multiplikasi flora dan fauna rumen (Payne, 1977).
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