اثر جنوب غربی : تجزیه و تحلیل سری های زمانی بر روی مسافران انتقال داده شده از طریق راه های انتخاب شده و مقایسه سهم بازار

The Southwest effect has been known for some time in terms of the US airline's impact on pricing, competition and traffic volumes. But recent estimates of the impact on traffic and market shares do not exist. This desideratum can be addressed by applying autoregressive integrated moving average (ARIMA) models with intervention analysis to key domestic air routes in the USA, where Southwest has started service. The paper first deals with the choice of routes to be examined and, after a preliminary statistical description of these, applies ARIMA models. These results are examined for both their statistical qualities and their reasonableness and the impacts are compared to those previously determined in the same way for Ryanair's routes from London.

This paper is concerned with identifying the impact of Southwest's start up on traffic volumes and airline market share on a variety of US domestic city pairs. Autoregressive integrated moving average (ARIMA) modelling with intervention analysis is used to estimate the impact of Southwest's start of service on route traffic. A comparison of this with actual market shares enables inferences to be made on the impact on competitors. Previous published work (Pitfield, 2007a) has been able to demonstrate, using the same modelling approach, what the impact of Ryanair's start up of service from London Stansted (STN) has been on competing airlines flying from other airports in the London system to either the same airport as Ryanair but more usually to an airport that is not thought of as a secondary airport. The impact is considerable. Passenger numbers grow on the route as a result of the start up and Ryanair at least captures that growth and normally has an impact on existing carriers by taking some of their share of the market as well. Southwest's impacts and shares can be compared to Ryanair. The impact of Southwest on prices (Morrison, 2001) and its competitors is so well known it has long been referred to as ‘the Southwest Effect’ (US Department of Transportation, 1993; Richards, 1996) with evidence being seen at Baltimore–Washington International (BWI) Airport (Phillips, 1996) and again at Denver (DEN) Airport Business (2006). Although estimates exist of the impact on traffic in the past papers of Windle and Dresner (1995), Dresner et al. (1996) and Vowles (2001), there are no recent estimates1 and a current estimate of the intervention effect on passenger numbers of Southwest, and its market share on the routes will enable comparisons with these past estimates and with the Ryanair impact previously determined. In addition, it will allow impacts to be determined for a much more mature market situation when the most recent start-ups are examined. US Bureau of Transportation Statistics Form 100 data are available online on a monthly basis from 1990 (Bureau of Transportation Statistics, 2006). These details origin–destination passengers carried between airports by airline and ARIMA models can be applied to these data before the start up of Southwest on routes when its impact can be estimated.

Similar ARIMA models are developed for each of the chosen corridors. The results show the significant impact of 9/11 in allcases and the significant impact on size of Southwest’s start up in two of the five cases at around 20%. How do these impacts compare to those found in other empirical work? Are these results in accordance with past work? Table 14 illustrates the paradigm of interpretations of effects giving the datum of market share and the estimated impact on size. It shows that Southwest is in the last two rows of the table either taking traffic entirely from competitors, as its entry does not grow the market, or growing the market and keeping that traffic. Ryanair is in the first category where it grows the market and takes share from competitors. It has significant and often larger impacts from market entry. The impact of Southwest is less than that found for the majority of routes examined in Pitfield (2007a) for Ryanair.Exceptions are Stockholm and Hamburg’s start up impacts. These are lower and of the order of 10% and these might be argued to be comparable to the Southwest routes in terms of scale and market segment but the impacts on Venice, Pisa and Genoa were estimated at 26, 30 and 44%, respectively. What reasons can be used to explain this difference?First of all, the Italian destinations analysed are more likely to be dominated by leisure traffic than the US cases, with the exception of Las Vegas. However the Las Vegas service has only been in place for just over a year so it may be too early to assess the true long-term impact of Southwest. Second, the number of carriers on the routes is higher in the US cases than the European and the scale of traffic is considerably higher on all corridors except London–Stockholm. Third, Ryanair, with its frequent offerings of flights at £0.01, as they appear on the website at this time, where taxes and charges are excluded, may be a more aggressive competitor. However an examination of fares being offered on two routes with similar stage length, 4 months from the time of writing (August 3, 2007) shows that the Ryanair return fare with all taxes and charges was £118 or $217 whereas the Southwest promotional fare was $246 or £134. In this case Ryanair is only fractionally cheaper so its ‘normal’ fares do not indicate any competitive edge but its reputation and its non-inclusive fares may. For all these reasons, it might be concluded that Southwest, when it has significant effects, has a smaller initial impact than Ryanair but that Ryanair establishes larger market shares as a result of its impact on competitors. It appears that the major US competitors are more competitive than most of Ryanair’s competitors in maintaining share through pricing and product differentiation. Finally, the explanation for the different estimates might be based on the different levels of network maturity and familiarity with low-cost service and this topic could be approached empirically using Gini coefficients ( Huber, 2005 ). This might be why the Ryanair impacts are higher than the Southwest impacts established using the same time series methodology.As for the comparison with the previous estimates for South- west, focussing on the change in traffic at the airports where Southwest operates, the approach previously used, is likely to give more dramatic impacts than when the whole corridor is examined in what Vowles (2001) might call routes between multi-airportregions and the estimated impacts are in keeping with the simple examination of the data.