American presidents have a 20-year death cycle?

A detailed analysis has revealed that with one exception since 1840, US presidents who have been elected in years ending in '0' have either been assassinated or have died of natural causes while in office. This 20-year death cycle has been recognized for many decades. An edition of Ripley's Believe It or Not, published in 1934, noted the coincidental 20-year pattern of presidential deaths between 1840 and 1920, with question marks inserted for the upcoming 1940 entry. This implied that there could be a continuation of the cyclic pattern, which was fulfilled when Franklin Roosevelt was re-elected in 1940 and subsequently died in office in 1945. Based on this 20-year death cycle, many astrologers correctly predicted the death of President John F. Kennedy when he was elected in 1960. Similarly, it was expected that President Reagan would also die in office, a prophecy that was almost fulfilled with the attempted assassination on March 30, 1981. Even more strangely, two Presidents, who were elected in years ending in ‘0’ - Lincoln and Roosevelt - both died in their following term after being re-elected in the ‘4’ year. Thus, the 20-year death cycle anticipated the successful re-election of these presidents. Curiously, George W. Bush was elected in 2000 and again in 2004. It is worth noting that presidents who were elected in a '0' year and died in office have all died in years ended in ‘1’, ‘3’ and ‘5’. Based on this trend, Mr. Bush's enemies would have been celebrating the news of his demise in 2005. But we all know that George W. is still alive and kicking. So what happens to the 20-year death cycle?