is_multi_author

 * @return bool Whether or not we have more than one author
 */
function is_multi_author() {
	global $wpdb;

	$is_multi_author = get_transient( 'is_multi_author' );
	if ( false === $is_multi_author ) {
		$rows            = (array) $wpdb->get_col( "SELECT DISTINCT post_author FROM $wpdb->posts WHERE post_type = 'post' AND post_status = 'publish' LIMIT 2" );
		$is_multi_author = 1 < count( $rows ) ? 1 : 0;
		set_transient( 'is_multi_author', $is_multi_author );
	}

	/**
	 * Filters whether the site has more than one author with published posts.
	 *
	 * @since 3.2.0
	 *
	 * @param bool $is_multi_author Whether $is_multi_author should evaluate as true.