我看的是11版，里面提到“assume that technology is proportional to
the level of capital per worker in the economy overall, \[A = \alpha * K/N = \alpha * k\]”，也就是说\[\alpha\]作为参数，那么在接下来说明\[y/k\] is constant:
\[y/k = F(K,AN)/K\]
因为F()是 constant returns to scale, 所以
\[F(K,AN)/K = F(1, AN/K) = F(1,\alpha)\]

因为\[\alpha\]是参数，所以\[F(1,\alpha)\]是常数，
把这个常数定义为a, 那么:
\[y/k \equiv a\]

谢谢