// EDIT: Cache the text elements. This is very time consuming.
    var texts = $('[data-type="scroll-text"]', $self);
 
    // EDIT: Also a bit faster than querying the DOM each time.
    var speed = $self.data('speed');
    var offset_y = $self.data('offsetY');

    // When the window is scrolled...
    $(window).scroll(function () {

        // EDIT: Cache the scroll top. Much cleaner and a bit faster.
        // You want to optimize scroll listeners as much as possible.
        var scroll_top = $window.scrollTop();

        // If this section is in view
        if (scroll_top + $window.height() > topOffset &&
            topOffset + $self.height() > scroll_top) {

            // Scroll the background at var speed
            // the yPos is a negative value because we're scrolling it UP!                              
            var yPos = -(scroll_top / speed); 

            // If this element has a Y offset then add it on
            if (offset_y) {
                yPos += offset_y;
            }

            // Put together our final background position
            var coords = '50% '+ yPos + 'px';

            // Move the background
            $self.css({ backgroundPosition: coords });

            texts.each(function() {
                var $text = $(this);
                var pos = (scroll_top / 10) * $text.data('speed'); 
                $text.css('margin-top', pos);
            });
        }; // in view
    }); // window scroll