the MCPON does not work alone. Assisted by a staff of three, the MCPON can also rely on the quality and experience  of  the  Fleet  and  Force  Master  Chief Structure and the Command Master Chief Program. Although  the  MCPON  continues  to  be  in  paygrade  E-9, he or she will receive an increase in pay while serving as  the  senior  enlisted  Navy  member.  If  placed  on terminal  leave  pending  retirement  immediately following   completion   of   service   as   MCPON,   the member  is  entitled  to  the  higher  pay  rate  up  to  a maximum of 60 days. The same compensation applies to the other senior enlisted representatives, such as sergeant major of the Army, chief master sergeant of the Air Force, and sergeant major of the Marine Corps. RATING  STRUCTURE When the United States Navy was in its infancy, there were half a dozen ratings. Before World War II, there were approximately 30. This number grew to nearly  200  before  the  war  ended.  Today,  the  enlisted rating  structure  is  composed  of  70  different  ratings. To make sure the rating structure remains up to date, the Navy conducts an ongoing study of its professional and technical needs. The ratings you will read about in this  chapter  today  are  likely  being  studied  and researched for possible changes tomorrow. As you read this  training  manual  (TRAMAN),  and  as  the  Navy continues to downsize, ratings are being combined. Do not be surprised to find out that some of the ratings discussed  in  this  chapter  will  have  been  combined  by the time you receive this TRAMAN. RATINGS AND RATES Navy enlisted personnel are placed in categories according to their occupations, known as ratings. In fact, a rating is like a job title, such as Engineman, Legalman,  Aviation  Ordnanceman,  Gunner’s  Mate,  or Sonar   Technician. Within  each  Navy  rating (occupation),  the  rates  (paygrades)  reflect  different levels  of  aptitude,  training,  experience,  knowledge, skill, and responsibility. Often, you will hear the words rate and paygrade  used  interchangeably.  Whereas  the words rate and paygrade  can be used interchangeably, the word rating specifically  refers  to  the  occupation  or job and not to a level within that occupation or job. In the  following  section,  let’s  examine  how  the  Navy groups its ratings. Let’s take a brief look at each of these groups. Ratings The Navy’s ratings are grouped into three main categories: (1) general ratings, (2) service ratings, and (3) emergency ratings. Let’s take a brief look at each of these  groups. GENERAL RATINGS.—  General ratings identify the occupations or job titles of Navy enlisted personnel in  paygrades  E-4  through  E-9.  They  provide  the primary  means  of  identifying  billet  requirements  and personnel  qualifications. Because  of  occupational similarity, a few of the general ratings will merge or compress at paygrades E-8 or E-9 to form a broader career  field  for  members  of  these  ratings.  This  provides for  progressively  higher  levels  and  scopes  of  authority and  responsibility. Appendix  A  of  the  Manual  of Advancement,  BUPERSINST  1430.16,  displays  the path of advancement for ratings, such as AE and AT, that compress or merge at the E-8 and E-9 level. SERVICE  RATINGS.—   Service   ratings   are subdivisions  of  certain  general  ratings.  By  identifying required   specialization   and   specific   areas   of qualifications in the use and training of personnel, service  ratings  permit  optimum  use  of  personnel^- and economy  of  training.  Ratings  such  as  Navy  Counselor (Counselor)  NC(C),  Navy  Counselor  (Recruiter) NC(R),  Aviation  Structural  Mechanic  (Hydraulics) (AMH), and Aviation Structural Mechanic (Structures) (AMS) fall in the category of service ratings. EMERGENCY RATINGS.— Emergency  ratings are  required  only  in  times  of  war.  Emergency  ratings represent  special  career  fields  encompassing  skills  or qualifications  that  do  not  require  identification  as  ratings during  peacetime.  Currently,  the  Navy  does  not  have any  emergency  ratings. For detailed information on each Navy rating, you should consult volumes 1 and 2 of the Manual of Navy Enlisted  Manpower  and  Personnel  Classifications  and Occupational   Standards,  NAVPERS   18068. NAVPERS  18068,  Volume  1,  has  an  abbreviated alphabetical  listing  of  all  Navy  ratings.  NAVPERS 18068, volume 2 contains the titles and abbreviations of all the Navy ratings. Volume 2 will also show you the service  ratings. You   can   find   a   more   detailed explanation of general, service, and emergency ratings in  chapter  1  of  the   Manual   of   Advancement, BUPERSINST  1430.16. Rates Within  each  Navy  rating, performance and responsibility. there  are  levels  of Each represents a 2-5