Getting data from using $wpdb from my created table

This should be simple. I copied and pasted the below code from the codex page on $wpdb into a template and it returns the correct $user_count variable:

<?php
$user_count = $wpdb->get_var($wpdb->prepare(“SELECT COUNT(*) FROM $wpdb->users;”));
echo ‘<p>User count is ‘ . $user_count . ‘</p>’;
?>

I’ve created a table (wp_designers) and tried to call exactly the same query as above on this table but it returns nothing:

<?php
global $wpdb;
$user_count = $wpdb->get_var($wpdb->prepare(“SELECT COUNT(*) FROM $wpdb->designers;”));
echo ‘<p>User count is ‘ . $user_count . ‘</p>’;
?>

Can someone please tell me what I’m missing?