The last we heard from Sony, the PlayStation 4 had sold 18.5 million units to consumers. This was at the beginning of January. Today, Sony revealed that the PlayStation 4 has sold over 20.2 million units to consumers around the world as of March 1.
"We are so grateful for the enormous support from PlayStation® fans worldwide, and we are truly humbled that gamers around the globe have continued to select PS4 as the best place to play," said Andrew House, President and Global CEO of Sony Computer Entertainment Inc. "We remain steadfast in our commitment to deliver unique and interactive entertainment experiences powered by the network and the PS4 system's deep social capabilities."

Again, that is sold through to end consumers, not just shipped to retailers.