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本文以1997年1月到2005年9月在伊斯坦布尔股市(ISE)上市的公司为主要对象,对其中的认证公司和非认证公司的月度收益及收益的差异情况进行了对比研究,同时也对土耳其认证机构和外资认证机构所认证的公司月度收益和收益波动情况进行了比较。对每年、每两年、每三年和每四年月度股票收益均值数据的分析表明:ISO 9000获证公司比未获证公司具有较高的收益率和较低的波动性。而且,对纵向连续年度收益率均值的比较分析也表明:获证公司的高收益、低波动具有持续性,有些年度的数据更是具有统计显著性。而土耳其本国的和外资的不同认证机构和 ISO 9000获证时间的长短对获证公司股票收益及其波动性的作用不明显。
This article compares the monthly earnings and earnings of certified and non-certified companies, which are listed on the Istanbul Stock Exchange (ISE) from January 1997 to September 2005. At the same time, Comparisons were made between monthly earnings and earnings volatility of companies accredited by certification bodies and foreign certification bodies. An analysis of the average of monthly stock returns for each year, every two years, every three years, and every four years shows that ISO 9000 certified companies have higher yields and lower volatility than unidentified companies. Moreover, a comparative analysis of the mean of consecutive annualized annualized returns also shows that the certified company’s high yield and low volatility are persistent, and some of the annual figures are statistically significant. However, the effect of the different certification bodies in Turkey and foreign countries and the duration of ISO 9000 certification on stock returns and volatility of certified companies is not obvious.