A risk analyst is evaluating the probability of default for a credit portfolio that includes two credit assets, one rated BBB and the other rated BB. The respective probabilities of default for these assets over the upcoming year are 3.5% for the BBB-rated asset and 4.2% for the BB-rated asset. Additionally, it is noted that the joint default probability for these two assets within the same period is 1.0%. Based on this information, what is the default correlation implied for the credit portfolio for the next year?