Is Daryl Harper the worlds worst umpire?

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I'm an Englishman and a cricket fan. As you may know we are currently playing the final test in a 4 test series in South Africa and are 1-0 up in the series. Now, in the previous test in Cape Town umpire Harper made at least 2 dreadful decisions that were thankfully overturned by the referal system. In this test in Jo'berg, Cook was given lbw to a ball that was clearly a no-ball. England refered and despite it being obviously a no-ball, 3rd umpire Harper has given it. With such a list of calamitous mistakes, should Harper lose his right to umpire test cricket? Statistically since the referal system has been introduced, he must also be the worst umpire given percentage of correct decisions given. What are your thoughts? Any other examples?