By The Numbers - part the sixty third

Here's a factoid question: don't look yet. Since the inception of the Summer Olympics, how many sports have been contested in all games? I bet you don't know. I sure didn't. ...
...
...
...
...
...
...
...
...
...
...
...
...
...

Only five sports — aquatics, athletics, cycling, fencing and gymnastics — have appeared in each of the 30 iterations of the Olympic Games. Others, such as croquet and karate, have had much shorter Olympic runs and were discontinued immediately after debut.

As some sports pundit (no link, alas) bemoaned, 'how did 3x3 basketball get added? more important, why did 3x3 basketball get added?'). And, BMX bicycle racing, boys and girls?