In the last couple of article in this series we discussed google search trends when looking at relative search importance of “Pizza in (state)” and “Pizza in (city)” as they relate to all US states and the top 100 largest US cities. This led us to believe that search trends have been going down across the country, which suggested that, perhaps, pizza was not the best choice of restaurant. Today I want to talk about some bias issues with these previous search results and how I addressed them using geo-tags in search results.
Both of my previous posts clearly showed that the relative search importance of people looking for “Pizza in (state or city)” were overall decreasing, which I – perhaps too quickly – interpreted as a general lack of interest for pizza. However a friend made me realize that I was forgetting a huge part of potential pizza searches, mainly those associated with searches like “Pizza near me” or “Pizza near (insert landmark)”. Maybe it is people changing their search habits, not their love for pizza.
This means that what I was observing before was not a general decrease in interest for pizza but – most likely – a general change in the way that people search for pizza places. Since search engines are now extremely location-aware, it has become unnecessary to be so specific, and much simple queries, like “pizza near work” or “pizza close by” have probably become way more common.
To solve this problem I have changed my pytrends code to instead look for any searches that contain “Pizza” but only take into account searches done in every particular state. That way I am more truly measuring actual search interest in pizza that is not biased by a particular way of searching. This also solves the problem of accounting for searches for people unlikely to purchase pizza – since I might google “Pizza in chicago” but might never actually go there – so it is a win-win scenario in terms of bias reduction.
The first image in this post shows you the change in the one year moving average from the start to the end of the data and in this case, to my surprise, we see that for almost all states interest has been increasing. The states with the highest interest increases are Oregon, Virginia, Delaware, Connecticut and West Virginia, all states that rank high in their current number of pizza restaurants and their growth during the past several years.
The second figure shows you the google trends evolution for all the different states. Here we can see that West Virginia has the steadiest growth, and since this is relative interest, a steady move towards the upside implies that absolute interest is increasing (since the 100 measure has been reached repeatedly in the past) so we should prefer states where relative interest makes consistent highs relative to other states – like Oregon – where the net increase in net interest has been higher but higher touches of the 100 value are less frequent.
The square of the Pearson correlation coefficient can give us an idea of what the most stable increase of interest has been through time. Here we can see that Wyoming – which has only had a modest raise in relative interest – has done so at the steadiest pace among all the states. Idaho and Kansas have also had similar steady increases while the highest interest increasing states – like Oregon and West Virginia – have actually been around the middle in terms of their stability.
With this information I am now more confident that pizza interest in the US is alive and well – which matches my actual real life experience way better – and I think these results do point us to some key states where demand for pizza is expected to be greater or more stable. Using only free data, we have therefore narrowed down our possibilities and can now say a lot more about interest for pizza in the US. If past trends are to continue – big if – then the safest bets for a new pizza place are probably Wyoming and Idaho, given the high steadiness of their trends.
The above is however only observation and speculation, since we don’t have a proxy for restaurant success it’s hard to know if the above affirmations actually hold and if they do correlate with restaurant success. However, we have taken free data a long way and learned a lot about pizza places through the process! I hope you enjoyed this first journey!