Osbert Hood, president and CEO of Pioneer Investments, will join MacKay Shields in mid-January as president, said John Prom, senior managing director at Mackay Shields. The position is new. Mr. Hood will report to Ravi Akhoury, chairman and CEO, and assist in the day-to-day operations of the firm, said Mr. Prom. Pioneer is looking at both internal and external candidates to succeed Mr. Hood, who will leave the firm early next week, said spokeswoman Tara Pescatore.