US President Barack Obama, in the wake of the Newtown school shooting massacre, has launched the biggest US gun-control push in generations. He has taken 23 executive decisions he intends to take immediately without Congressional approval. These include improving the existing system for background checks, lifting the ban on federal research on gun violence, putting more counsellors and "resource officers" in schools and better access to mental health services. He has also urged Congress to renew a prohibition on assault weapons sales that expired in 2004, require criminal background checks on all gun purchases and pass a new federal gun trafficking law - long sought by big-city mayors to keep out-of-state guns off their streets. Here's a look at how the US outstrips other nations in civilian gun ownership