Ajai, there are 20 IIMs and all the IIMs shortlist candidates for the interview stage based on their own criteria, which may be independent of each other. The process may include Written Ability Test, Group Discussion, and Personal Interviews. Performance in the CAT examination is an important component in the admission process. IIMs may additionally use other factors such as the previous academic performance of the candidates, relevant work experience, gender and academic diversity and other similar inputs in shortlisting and ranking of candidates at various stages of the admission process. The processes, academic cut-offs and the weights allocated to the evaluation parameters may vary across IIMs. A work experience of 1 year might not make a huge difference. Atleast 18 months work experience will be helpful. If your 10th and 12th marks are lesser, one way to compensate would be by scoring 95 and more percentile in CAT and then having a diversified profile.