The world faces many daunting challenges: climate change, ethnic conflict, economic disparity. Add to that the Herculean task of categorizing the world's many female butt types and matching them up with the right pair of jeans. Old Navy's Booty Reader made a stab at this by retrofitting facial-recognition technology to examine ass photos. Now, Levi's is introducing a "revolutionary custom-fit system" that involved taking 3-D images of 60,000 backsides to break down ladies' derrieres into three types: slight curve, demi curve and bold curve. Under the banner "All Asses Were Not Created Equal," the jeans company pays homage to Nike's sneaker customization engine by calling its approach Curve ID. Levi's says its breakthrough approach eschews size in favor of shape. Isn't it always the case that the biggest advancements are sitting in front of us the entire time? Levi's says its butt-curve system works for 80 percent of women. (Kiss My Black Ads speculates here on who they might be missing.) Among the startling facts Levi's references is this eye-opener: More than half of women try on at least 10 pairs of jeans before finding one that fits.