Bolt improved upon his second 100 m world record of 9.69 with 9.58 seconds in 2009 – the biggest improvement since the start of electronic timing. He has twice broken the 200 metres world record, setting 19.30 in 2008 and 19.19 in 2009. He has helped Jamaica to three 4 × 100 metres relay world records, with the current record being 36.84 seconds set in 2012. Bolt's most successful event is the 200 m, with three Olympic and four World titles. The 2008 Olympics was his international debut over 100 m; he had earlier won numerous 200 m medals (including 2007 World Championship silver) and holds the world under-20 and world under-18 records for the event.