This study investigates the use and relevance of the most widely used test of English proficiency in the era of globalization, i.e. IELTS. It discusses different versions of the test along with their corresponding components. General Training IELTS Writing Task 2 is the central focus of the thesis, and as the result of the test directly impacts the future trajectories of the test takers' professions, the issue is of real life relevance and significance. The study concentrates on three of the scoring criteria included in the General Training IELTS writing rubric which are used to assess test-takers’ achievements on cohesion and coherence, lexical diversity, and grammatical range and accuracy. As the rubric attributes increases in these three measures solely to higher levels of proficiency in English and ignores the impact of such factors as age of the test-takers and their level of education, keeping proficiency level constant can be expected to result in a uniform performance on those measures. For this reason, groups of English native speakers (as homogenous groups with the highest possible level of proficiency) constituted the participants in this study who contributed to the written texts which were later analyzed as the primary data. It was attempted to see if they would exhibit invariably equal levels of performance on those three areas in their writing. In addition, the IELTS website openly states the so-called Standard English varieties spoken by native speakers in Britain, Canada, US, Australia, and New Zealand as the basis of its proficiency assessment. Analyzing texts written by groups of native speakers from those countries could verify the proposed validity of such claims.   The data used in this study consisted of texts written by English native speakers retrieved from the LOCNESS Corpus as well as some texts collected through two especially designed Google Forms. The texts later underwent automated textual analysis using an online program called Coh-Metrix to collect their textual features in the form of numeric indices on the areas of cohesion and coherence, lexical diversity, and grammatical range and accuracy. Those indices were then analyzed for statistically significant differences using such statistical procedures as ANOVA analyses, t-tests, and correlation studies. Findings indicated significant differences among different groups of English native speakers on the investigated measures. It is argued that IELTS not only fails to capture the contemporary realities around the use of English worldwide but also assesses test takers on expectations which are not met even by English native speakers. Due to the diverse use of English in professional as well as daily encounters in the age of globalization, it is most probable that a single way of assessing English proficiency fails to meet the requirements of every single context of English use, and it is more justified for recruiting organizations to base their proficiency assessment on more locally-defined norms and practices.