How does the NBA lottery work?

With the 2015-16 NBA regular season now in the books, it's time to look ahead at what comes next. For some teams, the NBA Playoffs are right around the corner, but for others, the focus will now turn to the NBA draft and the NBA draft lottery. The draft lottery can change a team's fortunes in a hurry with a bit of luck, but how exactly does it work?

In most sports organizations, like the NFL or MLB, the team with the worst regular season record is awarded with the 1st pick in the draft, while the team with the 2nd worst record is awarded the 2nd overall pick and so on and so forth. The NBA is different. In an effort to prevent teams from "tanking" and losing on purpose just to get a better draft pick, the NBA implemented the Draft Lottery in 1985.

The early version of the lottery featured random drawings of envelopes from a bin. Each envelope would feature one of the non-playoff teams on the inside. The first envelop drawn would receive the 1st pick in the draft, the second envelope drawn would receive the 2nd pick and on and on it goes. This system ensured that every non-playoff team would have an equal chance of winning the top pick in the draft. In 1987, the NBA amended the lottery to select only the first 3 picks in the draft. Starting with the 4th pick, teams would be placed in order of worst record to best - the usual draft format.

In 1990 the NBA implemented the weighted lottery which is still in use today. Ping-pong balls labeled 1-14 are placed in the lottery machine and mixed for 20 seconds before the 1st ball is drawn. After the first ball is drawn, the balls are mixed for another 10 seconds and the next ball is drawn. This process repeats itself until 4 balls have been drawn. The numbers on the balls drawn act as a combination, and in order drawn does not matter (i.e. a drawing of the 1-2-3-4 balls in that order is the same as drawing the 4-3-2-1 balls in that order). With 14 different balls, that leads to 1001 possible combinations. 1 combination is disregarded, while the other 1000 combinations are distributed to the 14 teams. In the chart below you can see how many combinations are awarded to each team.

Seed	Chances	1st	2nd	3rd	4th	5th	6th	7th	8th	9th	10th	11th	12th	13th	14th
1	250	.250	.215	.178	.357
2	199	.199	.188	.171	.319	.123
3	156	.156	.157	.156	.226	.265	.040
4	119	.119	.126	.133	.099	.351	.160	.012
5	88	.088	.097	.107		.261	.360	.084	.004
6	63	.063	.071	.081			.439	.305	.040	.001
7	43	.043	.049	.058				.599	.232	.018	.000
8	28	.028	.033	.039					.724	.168	.008	.000
9	17	.017	.020	.024						.813	.122	.004	.000
10	11	.011	.013	.016							.870	.089	.002	.000
11	8	.008	.009	.012								.907	.063	.001	.000
12	7	.007	.008	.010									.935	.039	.000
13	6	.006	.007	.009										.960	.018
14	5	.005	.006	.007											.982

For example, if the NBA gave the Bucks a combination of 5-6-7-8 and the first numbers drawn matched that, the Bucks would receive the #1 overall pick (I can dream, can't I?) After the balls are drawn they are returned to the machine and another four balls are drawn. If the combination drawn matches one from a team that has already been chosen, or if it matches the combination that was thrown out, the balls are returned to the machine and the process is repeated until a winner is found.

After the No. 1 pick is determined, the same process is repeated for the second and third pick. Once the top-three picks are determined, the rest of the draft goes in reverse order in terms of win-loss record.

The actual draft lottery is not televised and as a result people throw around conspiracy theories about how "rigged" the NBA draft is. According to Jeff Zillgitt of USA Today Sports the opposite is true:

The NBA uses a representative from the accounting firm Ernst and Young to oversee the process, which is conducted just before the TV broadcast of the event. The ping-pong selection is done in a separate room, and inside the room are NBA officials, reporters, Denise Pelli from Ernst and Young, representatives from each of the 14 lottery teams, a ping-pong machine operator and timekeeper. The people in the room are sequestered without communication devices until the No. 1 pick is revealed on the TV broadcast. Here is a video from last year's lottery. The league uses a ping-pong machine designed by Smartplay International, which makes lottery equipment for clients all over the world. Smartplay weighs, measures and certifies the ping-pong balls before the drawing, according to the NBA.

 This season, the Bucks are tied with the Sacramento and Denver for the 8-9-10 slots with a 33-49 record. When a tie occurs, the chances among all teams are split evenly if possible. if there is an uneven amount of combinations to be distributed, a coin-flip determines who will get the extra combination. Typically the 8th team gets 28 combinations, the 9th pick 17 combinations, and the 10th pick 11 combinations. In this case the 8 and 9 teams will receive 19 combinations and the 10th team will receive 18 combinations.
According to Brewhoop, the league is expected to hold the coin toss for these picks sometime on Friday. Lets hope the Bucks can get lucky and get the 8th best chances of winning the lottery. The 2016 NBA draft lottery will occur on Tuesday, May 19th.