and Tower Records, as well as over forty Independent retailers. In total, data from over four-hundred and ninety stores are collected each week. The singles chart is compiled over seven days and released every Friday at noon by the IRMA, while Midweek Charts are produced daily, but only released to IRMA members. It was announced that from 1 July 2006, downloads would be counted in the charts. They would also feature in their own chart in addition to being counted for the overall chart. Data was initially collected from iTunes, Vodafone, eircom, Sony Connect, Wippit and Bleep.com. Although IRMA estimated the size of the download market to amount to only 14% of the total market in 2006, this has increased in more recent years. In 2014, the Irish charts first included music streaming data and in 2018, music video streaming data was included for the first time. Chart achievements All information is from 1962 to the present and does not include charts printed in the Evening Herald newspaper. First Irish artist to debut at number one Dickie Rock & the Miami Showband with "Every Step of the Way" (1965) Artists with the most number one hits Source: Songs with the most weeks at number one Note: Songs denoted with an asterisk (*) spent non-consecutive weeks at number one. Source: Acts to occupy the top two positions Lady Gaga — "Just Dance" and "Poker Face" (two weeks in February 2009). Pharrell Williams — "Get Lucky" (with Daft Punk) and "Blurred Lines" (with Robin Thicke & T.I.) (one week in May 2013); "Blurred Lines" and "Get Lucky" (six weeks in May and June 2013). Justin Bieber "Sorry" and "Love Yourself" (one week in December 2015); "Love Yourself" and "Sorry" (seven weeks in December 2015 and January 2016). "Cold Water" (with MØ & Major Lazer) and "Let Me Love You" (with DJ Snake) (two weeks in August 2016). "Despacito" (with Luis Fonsi & Daddy Yankee) and "I'm the One" (with DJ Khaled, Lil Wayne, Quavo & Chance the Rapper) (five weeks in May and June 2017). Ed Sheeran "Shape of You" and "Castle on the Hill" (seven weeks in January, February and March 2017): "Galway Girl" and "Shape of You" (two weeks in March 2017); "Shape of You" and "Galway Girl" (five weeks in March and April 2017). "Perfect" and "River" (with Eminem) (four non-consecutive weeks in December 2017 and January 2018). Ariana