  We do a systematic analysis of the question of calculability of CKM matrix
elements in terms of quark mass ratios, within the framework of the hypothesis
of universality of strength for Yukawa couplings (USY), where all Yukawa
couplings have equal moduli, and the flavor dependence is only in their phases.
We use the fact that the limit $m_u=m_d=0$ is specially simple in USY, to
construct the various ans\"atze. It is shown that the experimentally observed
CKM matrix can be obtained within USY ans\"atze corresponding to simple
relations among phases of Yukawa couplings. Within USY, one finds a natural
explanation why Cabibbo mixing is significantly larger than the other CKM
mixings. In the most successful of the USY ans\"atze, one obtains in leading
order: $|V_{us}|=\sqrt{m_d/{m_s}}$ ; $ |V_{cb}|=\sqrt{2}(m_s/m_b)$ $ |V_{ub}|=
(1/\sqrt{2})\sqrt{m_dm_s/m_b^2}$ ; $|V_{td}|= 3|V_{ub}|$. We study the behavior
of this USY ansatz under the renormalization group.
