C++クラスのstaticはsizeofに計算されません

class MyParam{
  public:
    int a;
    static int b;
    int c;
    static int y;
    static int z;
};

sizeof(MyParam) = 8

int MyParam::b = 10;
int MyParam::z = 10;

int main()
{
  MyParam p;
  MyParam dest;
  p.a = 10;
  p.b = 2;
  p.c = 4;

  memcpy(&dest, &p, sizeof(MyParam));
  printf("sizeof(MyParam)=%d
", sizeof(MyParam));
  printf("%d %d %d
", p.a, p.b, p.c);
  printf("%d %d %d
", dest.a, dest.b, dest.c);
}

[xiaochu.yh@OceanBase036197 cpp]$ ./a.out 
sizeof(MyParam)=8
10 2 4
10 2 4