It’s no surprise that retailers depend on strong Christmas sales but the global stats show and interesting story of growth.

Both the ABS and NAB show that retailers see a healthy lift in sales across December in the lead up to Christmas as well as continued high sales in January for post-Christmas rush.

Why is the Christmas period so important to marketers in countries like the US, the UK, and Australia? We analysed retail sales data and consumer surveys and we looked at the advertising performance from AdRoll’s 25,000 advertisers to find out.

Here’s what we learned.

Christmas holidays eat the other holidays for breakfast

Detailed retail sales data from the US shows the Q4 holiday season is by far the most impactful, with over $626 billion in sales— that’s a whopping 10x greater than the second-highest-grossing holiday, the back-to-school season.

In fact, when you combine the 2015 sales of all of the other US retail holidays tracked by the National Retail Federation, you get $156.8 billion—one fourth of Christmas holiday sales.

Retail sales increase 20–30% during the holiday season

Holiday_2016_ Infographic Charts_AUS-01News coverage of key shopping dates in the holiday season focus on long lines and packed department stores, but what impact do holiday sales actually have on the retail industry?

Across the three countries we looked at, sales during the 2015 holiday season rose 20–30% compared to average monthly sales.

For the US, the Christmas holidays resulted in approximately $626 billion in sales. Spending in December alone was 21.2% higher than average monthly retail sales throughout 2015.

The UK’s December, meanwhile, showed a 30.7% boost in retail sales—£44.8 billion—compared to the 2015 monthly average.

Finally, AU retailers saw approximately $63.6 billion in holiday sales between November 1, 2015 and January 15, 2016, which represents a 23% boost compared to the average monthly retail sales in Australia.

Ads get more clicks and conversions during peak holidays

Holiday_2016_ Infographic Charts_AUS-02As more consumers spend a greater amount on retail purchases during the lead up to Christmas, traffic rises on eCommerce storefronts and consumers are also more likely to click on ads.

We looked at the performance of advertising between November 26, 2015 and December 31, 2015, to learn how much more likely Australian ad viewers are to interact with advertising.

The click-through rate of ads rose 7.24% on average during the holiday shopping season. What’s more, the click-to-conversion rate (CTCR), which measures how likely users are to perform a desired action after clicking, like purchasing, rose 31.2%.

This means there’s not only a larger audience for marketing messages during the holidays, but also that these audiences are more likely to be swayed by advertising as well.

Christmas retail sales grow more important every year

The sales made at Christmas aren’t valuable for retailers raw sales alone; Christmas spending in itself is an economic trend that retailers are finding increasingly costly to ignore—steadily rising year-over-year in all the countries we looked at.

In the US, holiday retail sales grew from just under $500 billion in 2005 to $626 billion in 2015. In fact, 2015 brought a 3.5% increase in December sales for the US, a 2.3% rise in the UK and the biggest boost of 3.8% for Australia.

Globally the vast majority of Christmas spending is still in-store, but online spending is growing fast

Holiday_2016_ Infographic Charts_AUS-03The majority of holiday spending in the US—roughly 83%—still takes place in brick-and-mortar retail stores; however, online sales across all three nations have grown significantly faster.

In the US, the online share of retail sales has grown from 5.1% in the fourth quarter of 2011 to 7.5% in the fourth quarter of 2015. It is projected to reach nearly $334 billion in spending by the end of 2016.

Meanwhile, e-commerce in the UK has far outpaced the US, growing from 8.1% of all retail sales at 2011’s start to 13.3% in the first quarter of 2016. Slightly behind, Australia’s online sales represented 3.6% of all retail sales in 2013 and they are expected to reach 5.3% by 2017.

What Christmas means for the future of online retailers

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Online storefronts will face two tectonic shifts over the next several years: a rapid growth in market volume and an equally fast shift from desktop to mobile purchasing.

Online retail sales are predicted to reach $534.95 billion in the US by 2019, £86.96 billion in the UK and $23.94 billion for Australia at the end of 2018. Mobile, meanwhile, is expected to account for up to 43% of e-commerce sales in the US by 2019—up from 16% in 2013. Notably, during Q4 2015, 51% of online sales in the UK were completed on mobile devices. And with 63% of digital time spent on mobile devices in Australia a large proportion of sales are expected to be attributed to this channel.

Marketers wishing to take advantage of the Christmas season should begin planning in August and September. Digital marketing offers online retailers a wide range of tactics, like highly segmented display, email and search campaigns, to more efficiently convert increased holiday traffic. But it’s only through careful, advance planning that marketers can make the most of the Christmas boom.

To learn best practices for the season, try a few of these online resources: MailChimp’s holiday marketing has a comprehensive set of 100 creative and practical tips for holiday offers and marketing, Optimizely has created a guide to retail personalisation and HubSpot offers a great step-by-step walkthrough that explains the role email, blogging and social media play in Christmas marketing.