A credit risk analyst at Bank XYZ is tasked with assessing the credit risks associated with large corporations. To perform these evaluations, the analyst uses credit ratings provided by two different rating agencies, referred to as Agency X and Agency Y. The analyst has gathered data on credit ratings for 30 companies supervised by the bank. Each agency assigns ratings across four distinct categories, which are described as follows:

Rating categories	Description
1	High investment grade
2	Mid investment grade
3	Low investment grade
4	Non-investment grade

For a detailed comparison, the analyst has compiled a chart displaying the ratings given by both agencies to each company. This data is crucial in understanding how the ratings from the two agencies correlate with each other.

Corporate Ratings: Agency X vs. Agency Y

Given this information, the analyst seeks to determine which statistical method would be the most effective in estimating the correlation between the rating categories granted by the two agencies.