In Q3 of 2015, the percentage of spam in email traffic accounted for 54.2%, a 0.8 p.p. drop from the previous quarter. The Top 3 biggest sources of spam distributed worldwide were: the US (15.3%), Vietnam (8.4%) and China (7.2%).
A particular feature of Q3 was a new trick used in phishing emails – in order to bypass spam filters they placed the text of the email and fraudulent link in an attached PDF document rather than in the message body.
The full report is available here - https://securelist.com/files/2015/11/Q3-2015_Spam-report_final_EN.pdf