It's actually both, depending on the context in which "data" is uses. If "data" is meant to refer to a specific collection of numbers, then it is plural: "The data are in a spreadsheet." Replace the word "data" with "numbers" in your head. If "data" is meant to refer to a nonspecific collection of information, then it is singular: "The data on drinking and driving is clear". Replace the word "data" with "information" in your head. (Source: https://www.merriam-webster.com/dictionary/data)