Lok Sabha Election 2019: When exit polls got it horribly wrong

The voting for 2019 Lok Sabha Elections will come to an end on Sunday at 6 PM following which news channels will be allowed to do what they love most – broadcast exit polls. However, all exit polls need to carry the standard statutory warning – this might not reflect reality. In 2004, the exit polls though BJP-led NDA would return post the India Shining campaign and we all remember how hat turned out.

In 2009, the exit polls did predict a UPA win but failed to catch the swing in Congress’s favour, with the grand old party ending up with 61 more seats than it did in 2004.

Exit polls are exactly how they sound – people walking out of polling booths are asked how they've voted. That data is then added up to compute a party's possible vote share and from which a party's possible seat share is extrapolated.

In the 1999 elections, brought about by an early collapse of the Atal Bihari Vajpayee government some of the polls gave the NDA 315-plus seats while others said it would fall short of the half-way mark of 272... it finally ended up with 298.

In 2014 again, the  exit polls didn't completely pick up the swing in Modi's favour Most gave the NDA far less than the 336 seats if finally won.

Here are some of the other times the exit polls have got it wrong:

In the Delhi assembly election of 2015, no one quite gauged the size of the coming Aam Aadmi Party’s landslide. AAP was predicted to win between 31 and 53 seats in the 70-member assembly the range for the BJP was 17 to 35 the AAP finally won 67 seats. The BJP won 3

In Bihar in 2015, the exit polls predicted a 'tight contest' between the Mahagathbandhan and the BJP. The Grand Alliance of the JD(U), the RJD and the Congress finally  ended up with 178 seats in the 243-member house

And in Uttar Pradesh in 2017, an election fought less than six months after demonetization the exit polls predicted a 'hung house'. In the end, the BJP swept the election, winning 312 seats The full strength of the UP assembly is 403.

The big problem with exit polls is how they make the jump from vote to seat share, but that’s always the danger for pollsters in the first-past-the-post system.

But here's an example of how tricky it can get: In 2009, the Congress's vote share increased by just over 2%, but that worked out to an increase of 61 seats

That's the trouble. In the first-past-the-post system and when you have more than two parties contesting even a slight change in vote share can make predicting an election result very difficult

Finally of course, there is the fact that exit polls sometimes 'play up' certain sections of voters. That is, they seem to be more comfortable sampling the urban, rich, and upper-caste voter while ignoring the others.