Ken launched his transport manifesto today with what he called a "£1000 travel voucher" to "save Londoners on average £1000 over four years" in fares, aptly dubbed "Monopoly money" by the Lib Dems' Caroline Pidgeon. "Keep hold of this voucher so that you have physical evidence of my promise to cut your fares," said Ken. "A link on the voucher will take people to a 'ready-reckoner' on my website, where they can calculate exactly how much they will save."

This stunt is sensationally cheesy – I can already imagine all Ken's trusting young campaign workers printing out his "voucher" and solemnly carrying it around in their wallets, like South Sea Bubble share certificates or Greek government bond coupons. Do you remember that scene in The Hitch-Hiker's Guide to the Galaxy where the Golgafrinchans suddenly decided to make the leaves off the trees legal tender, stuffing large quantities of them in their purses?

Alas, at the time of writing there appears to be neither a link nor a ready-reckoner to calculate your "savings" – presumably because Ken's skilled computer technicians are still trying to work out an algorithm for lying. So I have taken the trouble to check Ken's figures.

As I've pointed out before, the claim of £1000 savings over four years for the "average Londoner" is fantasy. Ken himself has stated several times, including today, that his fares cut will cost TfL £270 million a year, a total of £1.1 billion over the four years – a figure also accepted by TfL. Dividing this sum by 7.5 million Londoners produces an average saving across the four years of £149, or £37 a year, not £1000.

In his transport manifesto, Ken is more cautious, saying that "the average public transport fare-payer will be £1000 better off at the end of my mayoral term." I have taken the trouble to check this claim and it, too, is a flat lie.

In fact, as my tables below show, almost no public transport fare-payer in London will save as much as £1000. The only people who will are those who travel from Zones 5 or 6 into central London every day by Tube or rail in the morning peak hour. Every other daily commuter – the great majority – will save substantially less. And of course those who travel less regularly, in the off-peak, or mainly by bus will save less again.

The savings figures given in Ken's manifesto today bear no resemblance to reality. They are based on two false assumptions: first, that a daily commuter will buy 52 weekly tickets or 12 monthly tickets instead of one annual ticket; and second, that inflation will be incredibly high.

My savings calculations below are also based on a number of assumptions:

that Ken will break the habit of a lifetime and keep his promise on fares;

that Boris will raise fares by 2 per cent above inflation every year, in line with the TfL business plan (he has said that he might not do so);

that inflation itself will be at the levels forecast this month by the Office for Budget Responsibility (3.2% in 2012,  2.3% in 2013, 2.5% in 2014 and 3.6% in 2015. Inflation in each year determines the following year's fare increase.)

The saving in the fourth year has only been given for January-to-May in reflection of Ken's claim that people will be £1000 better off "by the end of my mayoral term."

 

Zones 1-2 Travelcard

Boris plan      Ken plan        Saving in year (Jan-Jan)

Now                            1168                1168

Oct 2012                    1168                1086               £20 (Oct-Jan)

Jan 2013                    1229                1086               £143

Jan 2014                    1282               1111                 £171

Jan 2015                    1340               1139                £201

Jan 2016                    1415                1180                £78  (Jan-May)

 

Total saving £613

 

Zones 1-3 Travelcard

Boris plan      Ken plan        Saving in year (Jan-Jan)

Now                            1368               1368

Oct 2012                    1368               1272                £24 (Oct-Jan)

Jan 2013                    1439                1272                £167

Jan 2014                    1501                1301                £200

Jan 2015                    1569                1334                £235

Jan 2016                    1657                1382               £92 (Jan-May)

Total saving  £718

 

Zones 1-4 Travelcard

Boris plan      Ken plan        Saving in year (Jan-Jan)

Now                            1672                1672

Oct 2012                    1672                1555                £29 (Oct-Jan)

Jan 2013                    1759                1555                £204

Jan 2014                    1835                1591                £244

Jan 2015                    1918                1631                £287

Jan 2016                    2025               1688               £112 (Jan-May)

Total saving  £876

 

Zones 1-5 Travelcard

Boris plan      Ken plan        Saving in year (Jan-Jan)

Now                            1992                1992

Oct 2012                    1992                1853                £35  (Oct-Jan)

Jan 2013                    2096               1853                £243

Jan 2014                    2186               1896               £290

Jan 2015                    2284               1943                £341

Jan 2016                    2414                2013               £134  (Jan-May)

Total saving  £1043